SoccerGeek, the general concensus is that "cooler running processors last longer," but if you aren't adding additional voltage even if you are mildly overclocking, you aren't going to be increasing the heat generated by much and the stock fan should be fine. If you plan to continue running at stock or on a mild (no voltage increase) OC, the stock fan should keep the processor running for much longer than you will want to keep it. Also, the stock fans tend to be significantly quieter than the aftermarket ones, and some of the aftermarket ones do not have the 4-pin connector and cannot be easily controlled via the mobo or software.

Sean