sorry total noob here... first time ever attempting to overclock...
Question: If I can get my i7 920 to run stably at 3.5ghz with the CPU & QPI locked to the stock voltages (1.2) on my Asus P6t Deluxe V2 mobo... will this do any harm to the CPU or mobo in the long run(or short run)? or is it better off having lower voltages than higher voltages because higher voltages create more heat which in turn shortens the lifespan of the CPU?
Higher voltages, frequencies, and heat all contribute to degredation (wear) on the CPU. However if your voltage is near stock, and the heat is reasonable, I doubt you will run in to problems, it'll likely outlast it's usefullness by a long margin.
In the unlikely event you get degredation problems, the solution is simply to lower the clock rate or increase the voltage slightly. The CPU wont just die, as this is a slow process.
In your situation i wouldn't have any worries or concerns myself.