Mine turned from a nude/beige to a reddish color. No deterioration that I saw but I use them only temporarily. They can get runs or ladders & allow media to leak out.
my dad told me he used to steal his moms nylon pantyhose for holding carbon. he never had problems with his tank. but he did recommend that you prolly should change it every 2 months or so.
^ I was about to do that yesterday, but I was too disgusted at the fact that other people's feet have been in there. I'd rather spend 2 dollars for media bags.