You're probably right or closer to the right value than I am. The reason I increased it to closer to x2 because when I train 2 positions I usually only get 5 players to get 48+ instead of the ideal 6. So you're losing training time to 1 player.
That's true, but there is also less risk involved. If you don't get your guy 48 minutes in the first game (fouling out or whatever), you still have a chance in the next games.
Run of the Mill Canadian Manager