I'm with Bmm...
Factually, they never "stop" growing. But at no point in their life can you say that they are "almost done." I have a pretty good-sized snake that was a runt for three years. I almost sold him many times, but never got the right offer (or good home). He looked like a two tear old at three, ate lightly, and then just took off. I'm still skeptical about beeding him, but he sure is a nice-sized animal now!