Car seats, in general, expire six years after their date of manufacturer. Upon expiration, you are to cut the harness straps and do everything possible to destroy the seat. I think I remember reading somewhere that they can be recycled too.
I am thrifty about a lot of things, but I don't cut corners with car seats.
The customer in the thrift store was looking at two infant car seats for her newborn grandchild. When asked about the price, the employee explained that since the car seats only had three point harnesses the price was donation only. The customer had no idea there was a difference between a three point and five point harness and was encouraged by the employee to look at another infant seat in the front of the store for comparison.
I stood there and watched the whole thing, trying to think of what to say. It occurred to me, however, that perhaps an expired car seat is better than no car seat at all.
As we were leaving the store, I saw the customer load the two expired seats into the back of her very new car. And I have to wonder if she was just trying to save a buck at the expense of her new grandchild or if she truly could not afford anything else.