I think that depends on what shape your clothes are in to begin with, and how many changes of clothes you bring along.
For example, I started out with some sport shorts that were well used. I replaced them about half way through, and the replacement shorts still have plenty of miles left on them. I started with new synthetic T-shirts, and they went all the way and are still getting use.
Generally speaking, clothing should go the distance. I suspect that if you need to replace anything, it will be because of a tramatic event, such as melting it when it got too close to the heat. Or they just get too grungy to wash and wear any longer.
Socks are another story. Probably what wears out socks as much as anything is the scree that gets into your boots. So, if you wear gaiters, that will reduce the amount of stuff that gets into the boots. And, if socks to wear out, just go into the next outfitter and buy another pair. No big deal.