How long can DS stay in the Maxi Cosi Priori XP?

[pipoca]

DS is 4 in march and weighs about 15kg (haven't weighed him for a little while, but he'd be 16kg absolute tops). He's currently in the Maxi Cosi Priori XP. When do I need to move him to a group 2-3 booster seat, in terms of safety?

When he out grows his current seat by height or weight (which ever comes first).

Also, while he is still fitting in his harnessed seat, try booster training him so that when he HAS to go in a booster he knows not to mess about with the seat belt, lean down and pick up toys, etc and why he shouldn't.

It might be worth getting a high back booster as a spare/emergency seat and going for a drive in a friend's car so he has a chance to get used to it and having to sit properly for the whole journey (you could start short with a trip to a local park for instance).

Errr, stupid emoticon..why should he not lean down and pick up toys etc in a booster seat? . What's the height limit for a group 1 seat?

if his eyes/top of his ears are above the back of the seat
or if he is over the weight limit for the seat (i think that's 18kg for the priori)

Because if he isn't seated properly at all times the seat belt won't protect him in an accident. Imagine what would happen if he was bending down with just the lap belt securing him and you had an accident. It doesn't bare close examination!

In a booster you are relying on the child to act safely and protect themselves.

In a harnessed seat (for the most part) you, as the parent, are responsible for securing them.

Height limits vary from one seat to another. Best check your manual for guidance.

until he is 18kgs or his ears are in line with the seat back