When is the car seat outgrown?

A rear-facing car seat with belt attachment can be used until the child weighs about 25 kilos. The seat is outgrown when the child’s head is sticking up by a third over the edge, roughly on eye-level of the child, or when the car seat’s recommended weight limit has been passed.
When the child has outgrown the car seat replace it with a booster seat and eventually a booster cushion. Both physicians and researchers recommend that children should use a booster seat or booster cushion until they are approximately 10-12 years old.