Re: is it time for different car seat?
EDDIE BAUER makes a good 3-n-1 that the kid can go in from 5-80lbs. VERY popular. there are two models, the higher-priced one comes with featurs like arm rests, etc. but is basically the same as the lower-priced one. (not too much price difference though). the locking system is different though, so maybe try your daughter in it and see which lock is most comfortable for you/her.when she reaches 40lbs, you take the harness system off the seat.
the booster seat is recommended for kids who are 40lbs and/or have reached the minimum height requirement. maybe your daughter is really tall? check your local laws to see what age/weight the child must be to be without a carseat. (in my area, its illegal if the child is not at least 80lbs, and there are some seats that go to 10lbs)
regardless, a convertible carseat is a good way to go.