[Christ]

Fix-a-Flat isn't foam in the sense that it ever hardens/congeals/sets... you could leave it in a tire for 2 years, and when you peel the tire off the rim, it's still liquid. It doesn't clog the valve stem at all.

If used properly, it temporarily seals SMALL leaks, like screws in the tire, bead leaks, dry crack leaks, etc.

It also throws the balance of your tire off significantly... and should be removed from the tire immediately.

A tire tech is more likely to throw your tire away if it never had F-A-F in it, but does have evidence of being driven on extremely low air pressure.

Evidence, for tires, consists of beads of rubber in the tire when you take it apart. You do not remount those tires, you remove them, dispose of them, and replace them.