General Forum

I think it is the quality of the sleeves. I use Ultra Pro. I purchase older collections and I've had to force cards out of penny sleeves. They did not seem to have any damage like as in bricking. On a side note I had a 2005 Verlander RC stored in a 9 Pocket Ultra Pro Page in Album for 14 years in a non climate controlled man cave down stairs. I sent it to PSA and got a GEM 10. My Trout RCs spent 7 years in the same environment and 7 out of 9 were GEM 10.

I’ve always bought ultra pro as well and they definitely stick to Chrome and Prizm cards after a while. It’s worse if they’re also in a binder or top loader than loose in a box but it does happen. Full disclosure my cards cards are in a climate controlled room but sometimes humidity gets a little higher than I’d like. 

I never had any issues but as a general rule of thumb it's always good to "refresh" your cards at least every 10 or 20 years. If you have cards from the 80s or 90s still in original penny sleeves, by now that plastic has started to degrade like most plastics do