I prefer Aida 64 Extreme but everyone has their own preferences. But the three main ones you hear in the Overclocking Community are Realbench, Prime 95 (Blend Test), Aida 64 Extreme. Yes and Intel Burn which I haven't used tbh. I use all three. I go no less than 4 hours with Realbench and Aida64. I ran them both for 4 hours then crashed an hour into the latest Prime 95, upped vCore .010v tried again hit 3 hours and been rock solid since.
Until I updated my Bios to version 3007 last Sunday. Had 3 freezes and 2 Blue Screen crashes. The last being at 2am last night. Flashed back to version 2202 put all my Overclock settings back how they were, ran Aida for 5 hours, been tinkering with 4.6 GHz all morning. Just hit the 2 hour mark with Aida at 4.6 GHz Core/Cache 1.32v in Bios/LLC level 7. Idle at 1.312v and 1.344v under load. Probably stay here.
Depends on what's "Stable" in your eyes and what you are using it for. Just Gaming, Aida 64, RB, or p95 version 26.6 for 4-6 hours will probably be fine. I was able to run all three of them at 1.296v for 4.5 GHz but Prime 95 version 28.10 Blend (I recommend running if you are going to be editing) I crashed 51 minutes into. I couldn't pass the 90 minute mark with anything under 1.328v. So I'm gonna run that next to make sure 1.344v is enough for 4.6 GHz because it is more demanding than RB and Aida.