You hear the "peaking too early" concern with many teams in many sports. I am not sure there is much you can do about it. When you peak it probably most dependent on overall team health. Is everyone 100% and playing their best. You can manage health and minutes to some degree but you can only do so much.
The only thing a team can do is play hard and try to win every game while being reasonable or practical about managing players health. In the end, it is better to be playing well and to have momentum. You can't tamp that down and then expect to pick it up just before the playoffs.
Most of the Celtics title teams started strong, back to the 60's.
My concern is too many minutes for our starters. I would accept an occasional loss while keeping the first 5 at around 30 minutes per.
It will pay off come playoff time, but Joe seems oblivious and given his insecure thin skin, I don't expect much change unless somebody gets in his ear about it.
Celts have made deep playoff runs every season and it takes a toll on the legs, we saw it with Tatum two years ago.