It's basiclly because that its the match preperation and playing matches that makes the team learn the tactic. When you don't have any matches for a long time, it goes down. Now one could argue that this is not realistic but the way that the game is coded, it has to work the same way during the holiday as it does during the season .
Hmm. Okay, thanks. What's the best way to get the formations learnt quickly? I cannot for the life of me remember how I got them all full. I've set both training to Tactics for pre-season, best thing to do?
Training: The " Tactic" schedule has nothing to do with it. It just makes the players focus more on stats like Off the ball, Anticipation etc.
What really makes it go quicker is to get the team together ( Team Cohession), Playing lots of friendlies( result in many matches and many days of match prep.) and using Tactics in the match prep.