How long brakes last depends on your driving style. If yours are making noises, you should check them out. You'll have to pull the wheels off and look at the thickness of the actual brake pad lining material. If the noise is coming from the brakes, you'll probably see evidence of it on the rotors by way of a gouge or some other roughness on their normally smooth surface. By the way, noises generally are not good and there's two trains of thought on how to deal with them: check them out when you first hear them or wait until something breaks and fix it then. Only problem with the second method is it generally costs more to fix by then.
Karl
