How do you know when your child is too tall for carseat?

[kotzally]

I have a 2.5 year old who is in a Britax boulevard some of the time and an Evenflo Triumph the rest. He is about 30 lbs. and 37 inches, how do I know when he has outgrown the Evenflo in height?

Also with the Britax the center strap is sooo short, is this the same with other Britax's? My 4 month old will be needing a new seat once he is out of his infant and I wondered if I should look into another Britax because of the strap issue....

Thanks,
Elizabeth