saving you the long explanation - the ability to field punts, and not let them drop, in and of itself is a WIN in field position battle, and over the course of an evenly matched game, can often mean the difference between having significant scoring chances, and not having them.
A fair catch, IMO, is better than letting it bounce dead randomly - and a punt is a dead ball, until it's touched - and therein is the risk/benefit. Because if you don't touch it, it's dead, as soon as touch it, it's live again. (In lower levels of football around the country, recent years, there's been a significant movement where teams simply don't punt anymore, and play 4 downs all the time, and others don't field punts and rush 11 men on returns. Hasn't really made it's way into top level college or pros)
As for returns, any positive yardage on a return, is gravy, IMO. Just catch the ball, and maintain possession without giving up ground, if you can advance - wonderful - not necessary. This is all my philosophy only.
I firmly believe, that a guy that can field a ball (meaning catch punts) is invaluable, and it's a skill that is completely independent of age/height/weight/experience. You can either do it well, and hone the basic skills, or you can't.