I've used them for a couple years.  The bottoms of the socks don't come white, but they didn't before either. :)

Since I wash in cold water I take and boil a bunch of them (I think 12-15 : 6c water, I usually double it) then use it as liquid soap.   I freeze half for use later; I'd rather make a big batch than frequent small ones.

I keep the liquid soap in the fridge since it seems to otherwise get a film that bothers me.