Define overclocked properly, a lot of people take that as a different meaning by different levels of speed, voltage, temps, cooling, etc.
Really I have yet to have a CPU die that I have OC'd. I suppose it also depends on the product and quality of the product in question, of course cheaper components will fade out and fail sooner than better quality/cooled components that are more up to the task for the long term.
Way too many variables for such a vague quesition, but considering any modern electronic product has a lifespan, be it a few hours or hundreds of years, if you stress it more, it will fail sooner. So, then taking that into account, overclocking would add stress, speed, heat, etc, yes eventually whatever you overclock will fail, and probably sooner than if left at stock. Odds are it'll be long gone out of your ownership when that happens, or no longer in use to fail due to more updated products having been released in the years since you had overclocked said product.
I could go on and on really, but I think ya get the point. Short answer, even proper overclocked (depends on definition and many different variables), yes...the products life will be shortened, might not be much, might never happen while you own it, or the next 10 people down the line depending on how far, how hot and how much voltage. But in the same instance, unless going for WR benches or running 1.8v through a 45nm processor, you won't really be able to know just by how much you shortened the lifespan of said product.
Hope that helps.
