Unless i have a injury i start to make substitutions After the 60th minute, unless i am losing hard and whant to change formation, but i normally wait until the half time.
my subs are normaly my wingers, my ST If they are missing a lot or If the game is already won, my MCs If i am playing a strong opponent and whant to control the midfield with fresh players.
If the game is very balanced, but i am winning i wait until the 85th, just to gaine the green.