Well, 4 years is the bare minimum safe practice recommendation for "graduation" to a
booster.... Please visit the page titled *Preschool -- Preteen* in my site (link in signature) for more details on whether or not your child is truly ready for a
booster
I personally have chosen to keep my child harnessed in an appropriately sized seat until while using boosters only for emergencies/travel. My daughter is now 6 years old.