Yep, on the back of the seat you'll see an expiry date somewhere. The typical car seats you buy at say Walmart usually have a 4-5 year expiry date from date of manufacture, higher end ones up to 8-9 years. It's basically the manufacturer saying that structurally the car seat will remain like new for that period of time, and beyond that the plastics start to degrade. Using expired car seats is an insurance no no if you were to get into an accident.