I'm sure it varies widely. I just toasted my Athlon Classic 700, and it took a few days. The system was acting flakey, and I toyed with it (lowering the oc from 820 down to native 700), but it was randomly hanging, failing POST, etc. Well, it turns out, when I upgraded a fan in the system (it's getting hot outside, and I wanted to make sure the system was cooled properly) I swapped the cpu fan hookup (to the "fan2" header), and the fan didn't turn. So, it took maybe 5 days to toast, even with our 90 degree days. (The case I use has a dedicated fan and hood that directs air onto the CPU, so even though the processor fan was down, there was still some airflow, so that probably stretched the fry-time. It's because of this hood that I wasn't able to notice the CPU fan problem, the hood covers it )