My DD is 4 months old but already 25 1/4 inches long and weighs 17 pounds. Her carseat only goes up to 30 inches and 30 pounds. So my question is when do I switch to a new carseat? When she's 30 inches or 30 pounds because I doubt it'll be at the same time. Also, what carseat did you use after your baby outgrew the infant carrier? She is really strong and sit up by herself already so I was thinking a convertible carseat, but not sure which one to get. Any advice on that also? Thanks!