My understanding is that they hold up great over the years, but you can't be really abusive to ANY bag and expect it to continue to look good. But normal wear should be fine.
If you get a light colored bag, some owners treat their handles with a protector called For Handles Only that prevents skin oils from darkening the leather...other than that, I haven't heard of any complaints. Most of my bags are current season bags, though, and even my 05 is brand new, so maybe a poster who has carried the bags for several years will chime in.