My experience has been that almost every time I missed 5 starts PRIOR to game 22, the guy has a cow. And most of THOSE times, the missed starts were due to injury, missed while hurt, but back in as soon as he reached 90%.
A few times, I've had guys who looked good enough to start for young teams but their play was terrible and I sat them a few more times than I should have, in this instance, every single time I hit 5 missed starts at less than 22 games, they have dropped in WE.
The times when I have sat a player who had been promised a start after game 21, for the remainder of the season, 2 for certain have complained, most accepted it, and no one has ever transferred after missing 5 -10 starts. I did have a guy once who's potential flamed out after 10 games who missed all the starts after that point because I planned on cutting him anyway and didn't care if he transferred. Even he didn't transfer. I did cut him though. I seldom make a promise I don't intend to keep, but the times when I have been unhappy with the result, I have only once had a problem if I waited until after game 22 to sit him. After game 21, you will have problems with SOME, but not all players. I did one time have a problem with a player who got sat down after game 23, but that has only happened once.