I seem to have reached some critical age on my bike. I went through many years, not needing to replace anything, and all of sudden it seems like parts are failing left and right. I replaced my first set of derailer pulleys this weekend. Just a few weeks ago, I replaced my first set of wheels and not long before that my first chain ring. I haven't a clue how many miles are on all of the parts being replaced, most of them have resided on three different frames now. I'm sure it's still cheaper than replacing car parts, heck I provide the labor, which I certainly can't do on my car.