I recall people going to 1.4V if the temps were under good control (less than 80 at all times under linpack or similar) although there was a lot of controversy about what was actually safe. I think ZealotKi11er's 1.35v is a very reasonable and sane limit.
If you are uncomfortable with it. 1.45v with stable temps and operation is probably fine. I ran my 980x at 1.4v for years. The motherboard ram controller broke but the processor was still fine after 5ish years.
You want to run the lower voltage possible that still gives you stability. If those maximum temperatures were under load, you should be fine. I don't remember how sensitive Nehalem processors are, but Westmere didn't like uncore voltage over 1.35V. That killed more processors than core voltage.
I mean, at this point in time are you really concerned with how much longer it lasts? It is already like 8 years old? I can't imagine you should be concerned about degradation this late in the game. In 2 more years phones will be faster than it. Honestly, i'd let it ride at that voltage now.
Honestly? These CPU's are on the edge of being worthless (I see them go for around e15-25) so I wouldn't really care about Vcore, they are also extremely hard to degrade/kill. Just watch the temps and OC at as high as you want.
I ran dual X5670's (SR2!) on 4.4GHz somewhere around 1.4V. Nothing wrong happened to them.
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!