Yes.
But normally overclockers replace their CPU before degradation occurs.
It's also a gradual process, so if you start to feel the effects you can back off to stock settings (e.g. it wont just die one morning).
Because CPUs degrade long after they're off the market, nobody can really provide accurate time frames. Some people are completely relaxed on the issue, other people say 1.45V will kill a 45nm CPU in a week (which I know is rubbish as I ran 1.5V for 3 months - no problems). So be wary on the topic, people often take their opinions on the extreme, it'll be up to you to make the decision and accept any related risks.
Heat is another big contributor too. We have users on here that undervolt and use aftermarket cooling to extend their CPU life (no overclocking). I'd (based on what I saw on Intel charts) expect those machines to last 10+ years. In my case, I'll replace the CPU within 12 months so I don't care.
Do searches for the term "CPU Degradation". That's the term that's used.
Hope that helps