For my first 30+ seasons, I kept a spreadsheet for each team. I've gotten away from it with player notes. I think PN is underutilized as the yellow notepad gives you an easy way to see what you once thought on the Edit Rosters screen.
I do promotions, deactivations, etc., on Saturday/Sunday mornings unless an injury/fatigue forces an earlier move. That's usually about every 20 games. Position players, depending on skill, are given 200-500 AB at a level and pitchers get around 25-30 appearances before I'll consider them for promotion.
My goal is to have them ready when they go on the 40. If they haven't made it when they can become 6 year FA, they probably won't make it.