When I had my E6750 OC'd to a mild 3.2 Gb I couldn't get it stable under 1.3625 V. As long as the temps are staying comfortable it should be ok but you need to run Orthos or Prime95 for a while to make sure that's the case.
A lot has to do with the board. The one he has mas tons of controls and its an X45 Chipset. Tons of features you don't find in most BIOS. My personal preference is nothing over 1.325 for a 24/7 machine, but it does depend on CPU voltage ratings. If I am shooting for some really high benchmarks I do go above my rule but it is not for 24/7 machine. I do my think and go back to normal settings.
For instance a Q6600 max volts from Intel on that chip is 1.325 but to get 4.6GHz our of it with a FSB over 2100 and scores in the 22 - 23 range I am a little under 1.4volts to the core but other CPU voltages are manually adjusted also along with the microvolts to the chipset and the relation voltages of the CPU to the chipset (not 24/7 safe).
Over 90% of my OCs are on Quads and they get real freaky with to much voltage. But most of them OC real well without to much pushed to them.
