As long as you keep within the proper limits of voltages, and of course temperatures, it should last a good while.
As a general rule, for every 10C a semi-conductor is hotter/colder, you half/double its lifespan. That sounds scary, but CPUs are remarkably well-built works of art and feats of engineering. The fact that your standard chip will easily last through an upgrade cycle or two (or three... or four) is a testament to that.
Overclocking is scary business - a lot can go wrong. If you're safe, and take it slow, you shouldn't experience much, if any, issues. The lifespan will be shortened - but just using your company does that. Any reasonable overclock you do should last you into the next upgrade cycle, at least.