As I learn more about 3D printing, it seems to me one of the most catastrophic failures is when the thermistor pulls out the hot-end, as it could cause the heating element to runaway and start a fire. I think that's why the the Kossel Pro hot-end has it epoxied on so well. Almost any appliance with heaters will have a 240C fuse right before the heating element in order to get certified. Why should a 3D printer be different? It would certainly make me feel better leaving a print running all night. It's probably tricky to get the right location and fuse temperature to prevent the head from being destroyed without causing a lot of false fuse failures. But for preventing a fire, I think just something conservative in-line with the input leads of the heater cartridge should suffice. What do you all think?