Way back when I first got my sunbeam snake I failed to use a thermostat with the under tank heater I had set up in her tank. Being a burrowing snake, I figured that if the substrate got too warm, she would burrow to another cooler end of her tank. I also didn't realize that the heat can build up to near oven like temperatures under 6in of eco earth. She ended up losing her tail tip since it was the thinnest part of her body and cooked the fastest.... thankfully she suffered no other burns but I feel guilty to this day every time I hold her and see the nub where the vet amputated her dead tail.
Needless to say, I use thermostats now.....