These socks are the only ones I have ever found that prevent my feet from freezing when I decide to strap on a pair of snow shoes and go out for 3-5 hours at a time to do some photography. They are extremely comfortable, and not insanely thick either. I've had socks before that worked fairly well but were a pain to try and fit into my boots, so the fact that these are fairly thin and manage to keep my feet warm is amazing.
They are extremely durable - I've had the same pair for close to 2 years now. I only wear them when I'm snowshoeing, though, so they've been used for maybe 100 hours total. Still, they're not expensive, so you could easily buy 2 or 3 pairs and they would last you forever.
I find they can get a little itchy after a while, and they definitely don't dry quickly if you manage to get them wet. So coupling them with some thin, water-wicking socks can be useful. The pair that I wear are actually toe socks. I can't find them anywhere anymore, but they're water wicking and help avoid blisters, so if you can find them they're great to put under these wool socks for long hikes.