... while others seem to get stuck in time?
You'd think that ANYONE could continue to improve throughout his career. He's surrounded by dozens of other players with different shot specialties and plays thousands of games with/against a big variety of abilities and styles. Plenty of learning opportunities.
So, why do some guys appear to be satisfied to mail it in after they make the big time, while others just keep getting better and better?
Or, for some, is it just a physiological limit?