I've been a PC guy until just a few weeks ago when I got my first Mac, which is absolutely the best computer I've ever used. But with a PC over the years, the build up and the clutter manage to clog up performance. Should I expect my MBP to run as fast as the day I got it in 4 years time, or will it suffer from performance deterioration? Am I going to have to do a clean install in a couple of years? I have a 2.2 SR 15'' MBP.