Wear and Tear: An expiration date ensures that if all signs of wear and tear are ignored by the owner, the car seat will still be disposed of in a timely fashion. If we sat down and calculated the average number of times a child will be buckled into their car seat during the first 5 years of their life, I think we would all be surprised. Any piece of equipment that is used frequently is subject to normal wear and tear but especially when its primary purpose is to restrain the forces of a little person. Typical use of a car seat could subject it to spills and messes, attempts at rocking and escaping, expressions of joy or frustration through kicking and banging and even the gnawing of straps by tiny teeth. It all adds up. You also might live in an area where the car seat is exposed to extreme temperatures. A car with car seat parked baking in the sun on a hot summer day might be the same car with car seat that sits is the parking lot at a ski resort all weekend long enduring sub-zero temperatures. Over time, micro fissures (small cracks) in the molded plastic shell are possible which can weaken the material’s resilience to impact. Lost and broken parts are another thing that can accumulate as the years go by. Nothing lasts forever and your child’s car seat is no exception to that rule.