How do you know this? I'm not saying you are wrong just wondering how you came by this piece of information.
I had a player increase his game shape from respectable to strong while playing 84 minutes last week while another player went from proficient to strong while logging 64 minutes.
Allegedly, the BBs have gone on record in the conferences saying that the optimal amount of minutes is 60-65.
My observations are that having your guys play 80 or 35 minutes will not necessarily hurt your game shape too much, but it might take a dent -- and therefore it's hard to maintain high strong or proficient form while playing 80 minutes on a regular basis.
Everyone is free to take all this with a grain of salt -- I certainly do, but the truth is somewhere close to that, and it's the best info that I can offer at this point.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."