I remember a player of my first season, a MC called Sanchez, that was in my team till the season 11 or 13... he was a FK scorer and did great contributions in my team, and the last seasons even with 1* and 2* he appeared in the comments trying and trying to do something, so, I guess if I would have trained him till 5* almost, the contribution would have been high.

The fact that a player still on fire or not, depend of internal limits, limits for a single player and limits established to keep your team inside some parameters -ex. don't have 5 players scoring 40 goals during a season- ...so, first, what matter is this internal % of dominance that a player have in relation with the other players of the team, then, what matters is to keep the player in a good quality to be able to face the rivals and have the enough advantage to shine.

Then what affects are the movements you do in your squad, as these new signings change the roles of protagonism of the players you have but, as in my case that Ive experienced many times, it is posible to find a player that for his high domination can't be eclipsed.