It's up to you, i guess it changes smth with players morale ;D not sure tho.. but since i've got max bonus my players don't lose so much morale even if they get 6 or 7 rating..
I've got alot of money on topeleven so i don't have problems giving max bonus to players with main team.
i keep low bonus on alt teams tho ;D As they sometimes strugle with low finances..