Very much along the lines of what fastdude said. 1st we assume you do it correctly, which I would say means you do only up to a point of some stability and thermal conditions are kept at a reasonable level. Then again even if not CPU's are very tuff. If we in theory say your CPU is likely to last 20 years and if you OC big time cuts it's life in half that still gives you 10 years which is beyond the usable lifespan for almost everyone here.
Having some experience on boards like this it is very rare that CPU's fail. It is almost always something else. They have built in safety features that prevent acute failure do to Thermal stress.
So will OC'ing your CPU reduce it's lifespan, in theory yes but realistically no. Happy OC'ing.