Not a dumb question at all!!
The 'life' of the foam is comparable to any urethane product out there. The inner foam, which you may think would be the major worry, is the same "species" as the outer, tougher rubber.
They will dry out/ crack/peel/age at the same rate as any basic rubber product.
The only real worry, is that even though it's sealed, the paint may one day start to rub off, crack, or flake. This will all hinge on use, enviroment, abuse, etc.
In other words . . . these should last as long as an unchewed doggie toy
Also, for those waiting on tracking, etc. start checking your inboxes at your paypal email's . . .I printed a bunch of shipping labels today!