I would call 8hrs+ Prime95 blend test stable.
You could also do an 8hr+ Small FFT Prim95 to ensure your CPU is stable but blend is the best as it tests all your ram. I found with my 720BE that it was the IMC and Ram that would fail on my overclock.
You could also do an 8hr+ Small FFT Prim95 to ensure your CPU is stable but blend is the best as it tests all your ram. I found with my 720BE that it was the IMC and Ram that would fail on my overclock.