Car Seat Expiration Dates

Do toddler car seats expire like infant car seats? My nine year old's car seat was manufactured in 1999, and he still needs to be in a seat because of his low weight. We haven't been in an accident, but I was wondering if we should get a new seat. And a booster wouldn't be a good option, because he likes his five point harness. I think that's because I have a bit of a speeding problem.