How long do you have to wait at the beginning of a season to promote a player to the ML in order to gain an extra year of control over that player? I have seen 22, 24 and 25 mentioned. Also is that referring to the number of days or the number of games? Thanks.

You can promote him after 20 days of the minor-league season (not games, and not based on when the major league team starts to play).

My rule of thumb: if your minor league season starts with the AM game on a Thursday, do your promotions after the AM game on the following Thursday.  If might be an extra day or two, but is easy to remember and takes the math out of the equation.

If you plan on making a playoff run and the player is important to that goal, waiting 1/8th of the season, while playing 9-10 games against divisional foes, is probably a bad idea.   You'll have control of a player for 10 years.   If he's a 23 y/o position player, he'll be declining when that time's up.   Pitchers last a little longer but they also lose STM/DUR in their mid 30s.

Thanks. I appreciate the responses.