I buy all new socks, all at once, all one color (currently gray). After washing, just put them together. When one sock wears out, just keep the good one until another wears out, and put the newly mated pair into the mix. After I get about two years out of a dozen pairs of socks, it's time for new ones. BTW, if I had unlimited money, I would wear a pair of brand new socks every day. I love how they feel.
I think you've got a really good system there BM...definitely 100x more efficient than ours!