No need to train GS, just keep weekly minutes of each player in 55-70 min range.
I've seen many times, especially since I've been U21 coach and talked to a lot of local teams, that a lot of managers buy 2-3 players with above-average salary for their league and overplay them each week, giving them 90-110 minutes.
But in-play contributions from a 60k player with Inept Game shape are equal to a player with 20k and Proficient game shape, if skills are similar. So wouldn't it be better to have three 20k players with Proficient GS? If I take this example further, you are basically overpaying the first guy with Inept GS by 40k each week.