+1 on it being overkill and probably being a bit loud. That said, it would probably work fine if that's the route you really want to go.
Just from my experience, I have had the occasional computer fan wear out on me (usually the very small ones on graphics cards) but it seems like they often last a very long time even when run continuously.
On the other hand, I've had to replace several bath fan motors, especially at our old house that only had one bathroom. My guess is the larger axle of a bath fan probably results in more friction which may cause them to fail sooner. I'm sure the motor also draws more amps so it probably generates more heat than a little computer fan would.