This is almost embarassing, but I lost my last baby tooth at...19! The dentist yanked it. It was loose for years, but not super loose. I was a junior in college when the adult tooth started growing in. It was the right upper canine, FWIW. I think DS8 is following in my footsteps, he only has lost 6 teeth so far--including two (!!) he pulled out the other night (the two upper front ones, they were loose, but yikes!). He was a late teether and his baby teeth were huge--he's on "watch" from our orthodontist because there's so little space in his mouth already. Plus, the longer the adult teeth are in the gums, the stronger they'll be, so dont' consider this a bad thing. But feel free to consult your dentist for any questions--believe me, I do it all the time, as half my son's class already has retainers, as did his sister at that age.