When do I stop using car seat?

[Fooferella]

DS is 7 and he's 144cm and just over 36kg. Child car seat laws say that they are not necessary after these milestones.
I'm wondering if it's now safer for him to NOT be in a car seat. He still fits into his stage 3 seat (just) so I haven't questioned stopping until DS asked if we could stop using it.
Any help gratefully received!

I kept DS1 in until he was 150cm as that is the law in other countries. It is better for him to be in it as long as possible. At his height the seatbelt would still likely cut into his neck.

Thanks Lemon . That puts my mind at rest a bit that we can keep him in the car seat until he gets too big for it. At that point he will probably be around 150cm. This will probably be in about 2 weeks at the rate he's growing

Mine is 10 and in high backed booster.. he is very much in the minority.