Earlier quoted context omitted.
Children are more expensive now because of societal pressure to raise kids to a higher standard because people have less of them. Imagine all the hand wringing that would ensue if at lunch with my colleagues (which is a rough approximation of the HN demographic) I mentioned that I got a 5yo hand-me-down car seat instead of buying the latest and greatest. Generalize that pressure to pretty much every child raising rel…
It looks like a lot of car seat brands are considered expired starting at 6-ish years, so yeah, I wouldn't suggest using a 5yo car seat.
I know plastics become more brittle with age but a modern car seat that's expired is going to be tons safer than a car seat from 2000 (mostly because engineers now have better access to good simulation tools at lower cost). So what if little Jimmy isn't maximally safe. He's still a heck of a lot safer (from an unlikely edge case no less) than he would have been if he were born 15yr ago.