Enable WATCH_TEMP_PERIOD by default

Marlin/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/Marlin_main.cpp

       if (dual_x_carriage_mode == DXC_DUPLICATION_MODE && target_extruder == 0)
         setTargetHotend1(temp == 0.0 ? 0.0 : temp + duplicate_extruder_temp_offset);
     #endif
-    setWatch();
+
+    #ifdef WATCH_TEMP_PERIOD
+      start_watching_heaters();
+    #endif
   }
 }
 
     if (code_seen('B')) autotemp_max = code_value();
   #endif
 
-  setWatch();
+  #ifdef WATCH_TEMP_PERIOD
+    start_watching_heaters();
+  #endif
 
   millis_t temp_ms = millis();
 

Marlin/configurator/config/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/Felix/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/Hephestos/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/K8200/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/SCARA/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/WITBOX/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/delta/generic/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/delta/kossel_mini/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/makibox/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/example_configurations/tvrrug/Round2/Configuration_adv.h

 // If the temperature has not increased at the end of that period, the target temperature is set to zero.
 // It can be reset with another M104/M109. This check is also only triggered if the target temperature and
 // the current temperature differ by at least 2x WATCH_TEMP_INCREASE
-//#define WATCH_TEMP_PERIOD 40000 //40 seconds
-//#define WATCH_TEMP_INCREASE 10  //Heat up at least 10 degree in 20 seconds
+#define WATCH_TEMP_PERIOD 10000 // 10 seconds
+#define WATCH_TEMP_INCREASE 2  // Heat up at least 2 degrees in 10 seconds
 
 #ifdef PIDTEMP
   // this adds an experimental additional term to the heating power, proportional to the extrusion speed.

Marlin/temperature.cpp

 static void updateTemperaturesFromRawValues();
 
 #ifdef WATCH_TEMP_PERIOD
-  int watch_start_temp[EXTRUDERS] = { 0 };
+  int watch_target_temp[EXTRUDERS] = { 0 };
   millis_t watch_heater_next_ms[EXTRUDERS] = { 0 };
 #endif
 
       // Is it time to check this extruder's heater?
       if (watch_heater_next_ms[e] && ms > watch_heater_next_ms[e]) {
         // Has it failed to increase enough?
-        if (degHotend(e) < watch_start_temp[e] + WATCH_TEMP_INCREASE) {
+        if (degHotend(e) < watch_target_temp[e]) {
           // Stop!
           _temp_error(e, MSG_HEATING_FAILED, MSG_HEATING_FAILED_LCD);
         }
         else {
+          // Only check once per M104/M109
           watch_heater_next_ms[e] = 0;
         }
       }
   #endif //BED_MAXTEMP
 }
 
-/**
- * Start Heating Sanity Check for hotends that are below
- * their target temperature by a configurable margin.
- * This is called when the temperature is set. (M104, M109)
- */
-void setWatch() {
-  #ifdef WATCH_TEMP_PERIOD
-    millis_t ms = millis() + WATCH_TEMP_PERIOD;
-    for (int e = 0; e < EXTRUDERS; e++) {
-      if (degHotend(e) < degTargetHotend(e) - (WATCH_TEMP_INCREASE * 2)) {
-        watch_start_temp[e] = degHotend(e);
-        watch_heater_next_ms[e] = ms;
+#ifdef WATCH_TEMP_PERIOD
+  /**
+   * Start Heating Sanity Check for hotends that are below
+   * their target temperature by a configurable margin.
+   * This is called when the temperature is set. (M104, M109)
+   */
+  void start_watching_heaters() {
+      millis_t ms = millis() + WATCH_TEMP_PERIOD;
+      for (int e = 0; e < EXTRUDERS; e++) {
+        if (degHotend(e) < degTargetHotend(e) - (WATCH_TEMP_INCREASE * 2)) {
+          watch_target_temp[e] = degHotend(e) + WATCH_TEMP_INCREASE;
+          watch_heater_next_ms[e] = ms;
+        }
+        else
+          watch_heater_next_ms[e] = 0;
       }
-      else
-        watch_heater_next_ms[e] = 0;
-    }
-  #endif
-}
+  }
+#endif
 
 #if HAS_HEATER_THERMAL_PROTECTION || HAS_BED_THERMAL_PROTECTION
 

Marlin/temperature.h

 
 int getHeaterPower(int heater);
 void disable_all_heaters();
-void setWatch();
 void updatePID();
 
 void PID_autotune(float temp, int extruder, int ncycles);
 void setExtruderAutoFanState(int pin, bool state);
 void checkExtruderAutoFans();
 
+#ifdef WATCH_TEMP_PERIOD
+  void start_watching_heaters();
+#endif
+
 FORCE_INLINE void autotempShutdown() {
   #ifdef AUTOTEMP
     if (autotemp_enabled) {

Marlin/ultralcd.cpp

   setTargetBed(tempb);
   fanSpeed = fan;
   lcd_return_to_status();
-  setWatch(); // heater sanity check timer
+  #ifdef WATCH_TEMP_PERIOD
+    start_watching_heaters();
+  #endif
 }
 void lcd_preheat_pla0() { _lcd_preheat(0, plaPreheatHotendTemp, plaPreheatHPBTemp, plaPreheatFanSpeed); }
 void lcd_preheat_abs0() { _lcd_preheat(0, absPreheatHotendTemp, absPreheatHPBTemp, absPreheatFanSpeed); }