List of things I know, things I think I know, and things I don't know:
I know high stamina players (6+) tend to play 40+ minutes a game (assuming it's close) even with a sub, making it a challenge to manage game shape. I've seen Atrocious stamina players subbed out in the first three minutes before for a sub.
I think that I've seen low stamina players perform worse in the 3rd and 4th quarters of a game when they are set to play 48 minutes, but I have no statistical way to measure that.
I have no idea what stamina level equates to how many minutes one can play without having poor performance, ie: Proficient ST guys can play 48 minutes at the same performance level, while Mediocre can only play 34 minutes before seeing a decline in performance, etc... I'm not sure what the actual truth is.
I think a team of 4's and 5's is good, as it allows you to manage GS, and so long as you have subs, they should be fine in terms of performance throughout the game.