Law here is two and 30lbs, and even though he's hit that he'll rearface for a while longer. I'll switch once he's hit the max for his carseat rear, which is 40lbs. I've probably got another year at least, probably two.
My kids was all 1. I know alot of mom's who will hate what I said. My 11 yr old is in a regular seat belt my 7 yr old is in a blaster seat and my 3 year old is in a 5 point harrness
With my first I did it at 12 months. But he's 10 now and still in a booster seat because he's short. With the next two I turned them around at 4 years old. My 5 year old is still in a 5 point harness. And my 7 year old just moved to a high backed booster.