There is plenty of evidence in the films to suggest that they were in fact moving on with their careers and off the Enterprise. In TWOK, Chekov is XO on Reliant, and Kirk's line about having Sulu "at the helm for three weeks" suggests that the Ent is not his regular posting. Having everyone on the Ent-A in TFF is easily explained by all of their careers suffering some fallout from the events of TSFS. In TUC, Uhura references chairing a seminar at the Academy, McCoy wonders if they are being thrown a retirement party etc. Sulu has been in command of Excelsior for a number of years at that point also.
The only clear time in the films that all of our principals seemed to be permanently assigned to the Enterprise are in TMP, TFF, and TUC. TUC is clearly stated to be the last mission for that group on the ship.
I would suggest that McCoy's "If we're all here, where's Sulu?" when Sulu's been gone for three years (!) would suggest that most of the crew is no longer regularly assigned to the Enterprise in TUC, and have not been for some time.
Also that McCoy never checks facebook.
I've suggested this in the past (not the Facebook part.

The fact that McCoy asked where Sulu was doesn't mean that he didn't know that Sulu had a command. He wondered why, if the rest of them were present, why not Sulu?
The crew were scheduled to "stand down in three months." Who knows how long the ship had been back in spacedock with the crew on leave or interim assignments, waiting for their well-deserved retirement?