i have OC'd every cpu i have ever owned dating back from intel 486, pentiums, amd k6's, durons, athlons, intel core 2's and i5's. All of them lasted until they became obsolete, still running a core 2 OC'd in a HTPC. Stay within reasonable limits and you will be ok, although obviously there is always a risk. Reduce the risk by sticking to known safe voltages and temperatures, there are plenty of guides out there.