Pretty much. If you do everything correctly from the get go, you'll more or less have fully maxed out naturally after around 3 years. Anything you gain after that, will be minimal at best.
I put this on here a while ago and BigRo or whatever he's called attacked me because he didn't start gear before he was 25 and posted pics of himself at 5'10' and 165 to prove you can still gain after 3 years (look at those figures LOL. He was ripped though).