umm I've run Prime95 for 10 minutes with no errors, then had errors appear much later. I used to do 20 minute tests, but would find games would crash after about 4 hours of play. Another prime95 run showed an error after 1 hour of success.
If CPU thermal throttling was on, it shouldn't be a heat issue though. If it got too hot it'd throttle back, if it got to the damage point, the CPU would have shutdown. If the heatsink was so bad it couldn't control itself fast enough, it wouldn't have finished the boot sequence. The OP would've needed to disable this on purpose, and would require a slapping. (Edit: keyword "shouldn't" this could still be the case as El_Captain has pointed out)
We also don't know other voltage settings. It is...