Everything

My stability is usually 1M->8M->wPrime(both)->SuperPrime->RMMS->AOD 15 mins->Cinebench->AM3->2k6->2k1->Prime95 in-place large FFT 20 mins->5 hr gaming->Prime95 1hr30mins->Memtest.

That's on builds I only play around with like this one. 24/7 I stress it a lot more before calling it stable. Plus I don't accept temps near 55C if I can run lower and keep voltages low.