[glchen]

I had a card in the past, which looked like it had some kind of mold/mildew on it, and I've attached it here. I could see that mold or moisture being trapped within the holder could cause additional deterioration in the card since the water/moisture isn't able to evaporate as it would if the card were not holdered. For example, I remember reading in one of the soaking threads that you should not soak "X" type card because there were some instance where the card practically exploded after it was broken out of the holder.

For general staining issues, I think a lot of that is the card being misgraded or different "eras" or "graders of death (or the opposite) where some cards seem as if they definitely don't deserve the grade they got. I think that's the more likely answer to that instead of the stain got worse over time.

In general, I get all of the cards in my personal collection graded and holdered because I think encapsulation protects the card in most cases. For example, if you accidentally dropped the card or it fell out of a bookshelf and other books fell on top of it. In my case, I have three young children, so if they ever got a hand on some of my cards, there is definitely more peace of mind if they are holding one of my cards that is in a holder rather than just the raw card.