I had some of mine stored in books in a tote for a long time in storage at my moms. So I didn't have full control of them but now that I'm going through them some of the cards (maybe 3-4 of a full book) that were in the #1 spot had a slight arch to them in the top left corner. Not bad I think they will come back but it's noticeable. Also the top cards were coming out just a hair. Plus some with uv coating would stick and take a little work to get out but no paperloss.
just my experience. None of the cards were permanently damaged but I could see it happening in the worst of situations over super long periods if they get moved around and neglected.
like I said none were permanently damaged but watch out for the ones closest to the rings and the top row and store in climate control so they don't get stuck in there. It could all happen if they are forgotten and moved a few times.