its fine. the only negative side effect is noise. As far as longevity, if your fan speed is low, the temps are higher, so any benefit from running the fan at a lower speed is counteracted by the temperature the fan is exposed to IMO. And its a fan...they are cheap.
Thanks, my fan is really quiet (it has some sound absorber thing that i can't remember)
It's interesting cause I don't see much of a temperature difference if i run the fan at high RPMs... not sure if it's worth the stress towards the fan... it's half the price of my CPU! (The Athlon 240 only costs 40 bucks)
What about the exhaust fan in your case? How fast is it spinning?
If the exhaust fan is moving less air than the fan on the CPU, then some of that hot air that the CPU fan is blowing away from the CPU itself remains in the case. Meaning your exhaust fan is possibly "bottlenecking" your case cooling.