My DH loves his knitted wool socks, he likes them high up, nearly to the knees. I knit them for him, add an extra really fine wool when I make the heel and the top front bit to give it extra strength. So when they do get thin, mainly up the front I darn them and when I can't darn anymore because they really get too thin everywhere, then I cut them off around the ankle and just knit another foot to it with a same or similar colour. He's got them for years!!!! :P