Ok so my son is a year old and we have a Britax Roundabout. Now the one we have only holds a child up to 40 inches my son is already 31 1/2 inches. We just got the carseat in April 2009. Did anyone else have this problem, where they child grew out of the careset so fast! I thought I would get atlest 2-3 years out of it.
Re: Carseat Problem??!!
This is a guide on how to measure (which I was doing wrong until I saw it). HTH:
How to tell if your RF seat is outgrown by height:


It seems that how to tell when a RF (rear-facing) seat is outgrown is a fairly common question. It can be really hard to tell when a RF seat is outgrown, and a common misconception is looking from the front of the carseat to see if it is outgrown. The seat will pretty much always look outgrown from the front before it is truly outgrown because you need to look from the side.
This picture shows the correct way to measure. A line is drawn perpendicular to the shell/back of the carseat over the top of the child's head (#1). Then a second line is drawn out from the top of the shell parallel to the first line (#2).
Now measure the distance between the two lines. When there is *less than one inch*, the rearfacing restraint is outgrown by height.
This picture shows a common misconception with how people measure to check for the one inch rule. The line is drawn parallel to the ground from the top of the shell. You can see how this would appear to show the seat is outgrown, however it is incorrect to measure this way and this child still has room to grow in this seat.
The best place to measure how much room is left in the seat is when the seat is installed in the vehicle. They're usually more upright in the house and the more upright they are the more shell there will be above the child's head making your measurements not acurate.