I thought it may be worth revisiting this thread as I have just replaced the 7W resistor on one of my printers. This resistor was changed with a head redesign at least 5 years ago and the printer has done thousands of hours of printing with the same resistor. Changing the heater voltage from 12V to 24V also necessitated changing the resistor.
The original resistor was a Vishay Sfernice RWM6X22 vitreous enameled resistor. Other than showing the same discoloration as on the photo in the last posting, there was no damage.
Other than resistors sacrificed to engineering studies, no vitreous enameled wire-wound resistor has died on my watch while several heater cartridges have died and/or fried mosfets on controllers.
btw, earlier in this thread( [
reprap.org] ), DD said "Do you think a 3W resistor uses the same diameter nichrome wire that a 30W resistor (or a 30W heater cartridge) uses?"
In answer, it uses exactly the same size wire.
Mike