I prefer leather wallets but do they all leave this black tar-like substance all over the cards? I've had this wallet for maybe 5 years now and I can clean the cards, etc, and it'll still get this build-up or whatever it is. What is this crap? Also, do all leather wallets do this(I've had 3 leather wallets and all of them does this, though one was not bad)? Also, my DL is fading even though I rarely take it out.