Do they go bad over time? Digging thru my stuff, I came across a First Need water filter, and several spare filters for it. Probably going on 20 years old. Also a straw type filter, and another odd type filter I got at a gun show maybe 25 years ago.

Have a lot of trioxane fuel bars, maybe 20 plus years old.

And some store bought type bandages, dressings, military wound bandages etc. Some of the wrappers are turning brown, but still sealed, the military bandages are still in either the green or clear plastic.

Trioxane evaporates rather than goes bad. My "bad" bars just turned into empty wrappers. I've
moved on to different fuels since it's out-dated, nasty stuff, but if it's still solid in the wrapper it's
still good.

Bandages will still stop blood loss, but may not be sterile if the packaging gets pierced, which is
likely over time as plastics degrade. I usually rotate them out just to be safe.

No idea on the filters, I'd imagine the non straw types would be OK, especially if ceramic, I'd
worry more about plastic parts in the pump mechanism than the filters themselves.