I wear wool DeFeet and they get washed every day I ride. I have two pairs so if I don't wash my ride kit I have a clean pair.
I can get 4-6 months out of one pair, that is wearing them exclusively and then with darning them as necessary another 4-6 months. I will darn them until my wife yells at me to buy new stuff. Thankfully I do laundry and do not let her see them, one pair is a few good beer.
I will wash and hang them if I am camping. Clean socks and underwear are the most important things is what I was always taught.