How long is this car seat safe to use, and can I use a secondhand seat?

Stop using this car seat and throw it away 10 years after the date of manufacture, which can be found on a sticker on the back of the car seat. Graco advises against loaning, passing along, or purchasing a car seat secondhand unless you know the complete history of the product. If the car seat has been in a crash, it must be replaced immediately and not used again. (Page 18, 22)