Which part has done 15,000+ hours? My 172 has nearly 11,000 on the MR but in that time it has had new wings, tail, rudder, several engines, several coats of paint, etc. etc. and it flies and looks like a nearly new aircraft. Some of these old aircraft is like Grandfather's axe, you really need a good look through the maintenance logs before buying any aircraft, "new" ones can be worn out and "old" ones can be like new.