I believe most modern processors are pretty much built to OC now especially for moderate OCs. As long as your keep the temperatures in check, your lifespan will not be effected.
In my country OC isnt a popular practice. People keep telling me OC will reduce durability (lifespan) of my hardwares!!
It may reduce the life span of your hardware from 10 years to 8 years or something like that but at the rate things advance most people upgrade every 1-4 years anyway.