He's 22 running 10-15 minutes at full pelt in FG. Obviously sooner than we'd have liked or planned. If things go well he's got another 10yrs+ in the game, of course he'll be batter for longer stints. Forwards hit their straps late because it takes time to build that motor. Fifita used to be a high impact low minutes prop but matured into a dynamic work horse.
I think asking if a young player can improve is the definition of a stupid question. He's got a million dollar footy setup monitoring & driving & everything-ing him all day every day. In 3-4yrs he'll have turned the puppy fat into muscle, be wiser, fitter, more experienced, more stamina, still be a ****en monster though. We could have a NAS. But its just a pup right now.