Speed doesn't kill, voltage does. Crank the freq as high as it will go w/ voltages you are comfortable with. And try to keep temps in check. If you leave voltages on Auto, and crank the speed keep in mind that the board will automatically increase voltages...not good. Set things manually.
You can OC 20-30% on a lot of Intel chips using stock vcore or less. In this situation you are probably going to have a chip that lasts about the same as a stock chip assuming the same work load.
Even w/ high voltages, high clocks, and 24/7 intensive work-loads these chips will still last well past there useful lifetime. And since you have a K processor it should be covered under warranty even if you OC, so have some fun!