Can you train them really hard and play them in all games?
no, that's what i said.
No hard training and playing in games too but you can use them in two games every day.
If you see my team's roster, NIK, I have few players. It's only 3 good players in my bench.
I do also a daily training for the bonus (two sets of -6,75 cond. loss) too and use them in two games every day (with the use of 10-15 greens of course).
But i power-train them individually - meaning one day I 'll power train 2 players and bench them.
one -two days after, the same for another 1-2 players.
Doing rotation in power training.