for me there are two periods
- one is in the beginning, when I build a new team (many new players, training to increase quality)
then I wait, observing the weak points and players

-second is after the middle of the season, the 3rd week. The team is tired by playing almost every day two games.
Then there are two solutions. Rotation and maybe selling/buying 2-3 players
Playing only with the best so far performers - but not training at all.
Also try playing only defense/counters. 1-0 it's a victory too