There's no reason you can't gift a non-expired car seat, or even sell it. It's probably not a good idea to buy one on Craigslist, but we had no qualms about taking a secondhand car seat from a trusted source who assured us it hasn't been in any accidents.

Keep them and give them to family, otherwise donate to charity? Heck, check your local community chats/groups/forums, you can probably sell it for a small amount. Someone will find a way to resell it and make a profit.

There is a fear that car seats can be weakened by being involved in a crash.

My opinion is that it's way overblown, how many people have a serious crash with kids in the car? How many of them would then go on to resell the car seat? How many of those people would go on to have another serious crash to test the theory?

That said, when it comes to protecting our children, it's hard to justify saving a few bucks.

I remember sleeping on the windowsill behind the back seat of our car. Good times.