Play your trainees for more than 1 game, or be prepared to live with the loss of minutes is precisely what I follow. When it comes to training, it is advice I would give to anyone.
Sorry to pile on here, but in a one position training program, this is just a risk you have to take. The key is setting your line-up properly so that 95% of the time you get 48 minutes for your training slot.
He was just complaining that sometimes he ends up with 47 minutes for his best trainee. Sure, it is a fact of life that single position trainers have to live with. But with 47 minutes my advice would not be to play him in another game. The difference in lost training for your 3rd trainee is just not worth it.
Run of the Mill Canadian Manager