#1) have you checked for 24hr stability with orthos or dual prime95's?
#2) Well, OC'ing surely wont EXTEND the life of your components...
hehe but keep in mind that your mobo CAN handle CPU's that run taht fast anyways so OC'ing the CPU to the stock speeds of other CPUs shouldnt really make much difference to the mbob's longevity. As long as your not running that CPU redlined all the time it should outlast its usefullness.
But if 3.0GHz is its MAX speed, and you run 3.0GHz ALL the time. I give it a year, maybe, before you start having instability issues. You might only get 3 months.