If you care about the salary thing you can promote for the last 10-12 games of the ML regular season. Make sure he gets demoted before the ML world series ends, then promote after 21 ML days the following season.
You'll get him a few extra ABs for him at the ML level, he'll start the next season at the AAA salary, when you promote him he'll get the ML salary for only a prorated portion of the season, and the following season he won't accrue a full year. Win, win, win, win.