How does a player like Junior Paulo develop in the future?

I always wonder how these massive props such as Junior Paulo develop through their career.

Traditional knowledge of a prop is that they usually start to enter their peak in their mid twenties and are still playing at a high level into their early 30's. In their early 20's they can usually be quite ineffective as they struggle with the pure physicality required to play in First Grade.

However we're seeing more and more props who are able to crack grade at the age of 20 and are really starting to enter their peak a lot earlier. Junior Paulo & George Burgess being prime examples.

What I'm curious to know is how much development do they have left in them past their early 20's?
Do they have shorter careers than most other props?
Is there any value in them at 28-30yrs of age?
Can they play past 30?
At what age does their size become a hindrance and start to affect their mobility?