How does player progression work? It shows me their future rating but will they always reach this? In how much time will they reach this? Any help with player progression would be great.

Some notes:

1) There are boom players (those who exceed their potential) and bust players (those whose potential fall rapidly after they are drafted).

2) Coaches will help a player reach their real potential faster, but do not effect the boom or bust cycle.

3) There are certain attributes - strength, speed, acceleration, intelligence, passing arm, and passing release (I think) - that do not have a potential to increase that is shown. I'm almost certain that none of the attributes will improve. Although I'm certain that they do degrade over time.