I have Sealskin Socks and I've been wearing them for almost 2 years this december.
Aside from them getting dirty and starting to smell over time(probably after a year of using them a lot) I hand washed them and they turned out fine.. I even Machine washed them which isn't recommended and now they smell really good and they still hold water out for up to 3 hours which is pretty good for socks.

-Scott Lewis