We took it up at least to 1.79V, maybe higher -- can't really remember. Wasn't for very long, but the damage was fast and brutal. We're talking minutes of stability before totally fubar. Once we knew we had blown the chip we took it to the max possible to just see what it could do. Obviously nobody here should ever set a voltage that high if they ever want to use the CPU again.
I think we had it stable at around ~1.5-1.65V, but again, we didn't leave it at that voltage and just tried to crank the chip as far as it would go, so I have no possible word as to the long term viability of such a voltage. I think it lasted at least a few days at that voltage.
In retrospect, the entire thing was retarded. Just as a "post-mortem" follow up, that rig never ran stable, and we went through ~10 motherboards and a couple CPU's to get it decent (which it has been since). The Vapochill backplate shorted out all the boards, and in the process of trying to make it not short, the computer was ran with the Vapochill not entirely secured, which resulted in the CPU being operated in a literal pool of water. You can imagine how that turned out.
Anyways, to the OP: A reasonable overclock will probably be fine/not reduce your CPU life too much. You may want to read our thread, which can be used as an example of on how NOT to overclock your PC, before you do it though:
http://forums.anandtech.com/me...id=28&threadid=2173204
Don't do anything we did.
lol.