FYI, at those temps, you reached the limits. That's exactly what I experienced myself when trying to prime at 3.4 GHz, 1.4v and it failed after 3 hours (rebooted itself). The temps is hovering around 72C on the hottest core from CoreTemp 0.95. Since yours is bigger and lapped, you are able to push it further but obviously, we got similar results and we are just temp limited.

I guess that for 100% stability 24/7, we should try to keep it under 65C under max load. 70+C is on the borderline of stability, hence why Intel wrote a Thermal Specification of 71C in the docs, which might be the tripping point.

In my case, it's about the egg and the chicken because if I want to keep it stable, i need to raise the voltage but to lower the temp under 70C, i need to lower so I'm confused which one is causing crashes (too high temp or not enough voltage). For now, I will back down to 3.2 GHz for 24/7 use till I finish my watercooling setup. Your results gave me a good reason to invest in watercooling because I truly believe the G0 Q6600 can go to 3.7-3.8 on water for sure.

For sure, congratulations on your awesome results