My Venice seems to error at any temps over 50C, so I would have to agree that you'd want a sub-50C temp for 24/7 usage.
Any voltage that keeps you below 50C load should be considered, based on the OC you get out of it. At some point you're going to hit diminishing returns where cranking up volts no longer gives you a significant amount of clock speed increase, and I'd try pushing for that up to 50C-55C load while testing, and then settle back down to what works stable under 50C 24/7.
At this point, it does not look like you've hit diminishing returns yet, but given how quickly it ramped up, I'd bet you're pretty close to that point already. Sounds like you got a sweet chip, doing 2.8 at 1.4v. I haven't seen that too much (although I've heard rumors that AM2 chips are getting similar clocks at low volts).
FWIW, I have my Venice at 1.52v 24/7 and I load around mid-40s. It's only one core though, so no guarantee you'll be able to volt that high with temps that "low".