Do the cards within the graded slabs degrade or damage over time, lowering the grade
 

I know everything will eventually degrade or be damaged, but have we seen any of this in the time span that grading has been around, I believe since 1991. Have the cards within the slabs deteriorated or been damaged to lose a grade?
Just curious, if slabbing the 100+ million cards by PSA, BGS, SGC we are seeing data of maybe the slabs themselves having issues, such as yellowing or easily damaged.
Sorry about this question possibly wasting your time, but I do not know allot about grading and felt this was the best group of people to ask my novice question on this subject matter.

I had the same concern, mostly with the older cardboard that's got a lot of wood fiber.
Some degradation happens to that cardboard, but as with other items that are similar it's not well understood (maybe by the better conservators)

One thing that affects it is exposure to air. So for example, an old book from a period when they were using cheap paper, the page edges will brown before the areas closer to the center. And just for it to be contrary, degrading items that are in a sealed container have the opposite thing happen, where the acid produced by that degradation can't vent, and causes further degradation.

I also wondered about the slabs, thinking if they were sealed they might retain those acids, and end up causing problems fairly quickly.
I asked, and as far as I know, the slabs are not airtight. So those acids can to some degree vent and not be a problem.
Or at least, only as much as the typical storage boxes most of us use for non-slabbed cards. I have some that are well over 25 years old, older than grading and they have not caused any problems yet.

I'm no longer concerned about a regular card in a slab, and maybe a bit concerned about altered cards in slabs, or much older ones on acidic cardstock that are slabbed.

I wouldn't worry about it. I'm mostly pre-war and my cards are well over a hundred years old. They were stored who knows how for probably 80 years until they made it into a slab.

Yes I have seen a lot of cards that the slabs damaged. It is mainly badly cut SGC inserts damaging high end cards. I have seen it with the other slabs also just not near as much.

I have no idea if cards degrade in slabs.

Kellogg's 3D cards come immediately to mind

I swear those crack if you just look at them wrong....