Its your call really, if its not 100% stable but still maybe 99% stable then the computer is probably useable but you'll have to put up with more hangs than usual ones that windows tends to throw at you (thanks a lot, bill gates ). That might be ok for you, especially considering most of the errors only occur at full load-which is only for short durations for most users and even a fair number of gamers. The actual clockspeed of the overclock has minimal effect on processor lifespan, its more affected by voltage used and heat produced due to overclocking.

If you're doing real heavy stuff like video editing/3D studio then you might consider making sure its 100% stable-those can really load the proc to the max for an hour or more. Nothing like rendering a video for 3 hours only to have it fail at 95% and have to start all over again.

Thats not true bro, especially if you're using prime to check for memory errors. I've had prime run for over 17 hrs only to fail just before I was about to stop it. Once was due to processor, the others were due to memory.