If he can't get the teeth replanted, he's going to need new fixtures probably anually or more frequently for the next 10 years or so. It may start slowing down when he hits 17 or 18, but probably not before. There's a lot of growing to be done and the jaws go proportionaltly.
I recall my dentist saying he's replanted teeth up to 36 hours after, although the sooner the better.