Beginner's Guide to Athlon 64 Overclocking
 

Technically, an overclock that crashes after 8 hours is not 100% stable, but stability really is relative to the observer. If you depend on your computer to always pump out 100% accurate results in whatever you do (scientific simulations, for instance), you shouldn't be overclocking in the first place, but if all you ever do is play games and listen to music, 100% accuracy is not required. Personally, I generally aim for at least 20 hours of stable Prime95'ing. If my processor can survive 20 hours of extreme torture, it should be able to handle anything I ever throw at it. I'm a perfectionist in this sense, and I'm sure many people would argue that 6-10 hours is enough.

http://neoseeker.com/Articles/Hardwa...wto/index.html