As Who said, it's a balance. My guess is that Joe's thinking if it ain't broke, don't fix it. He's managed minutes all season, with only Tatum averaging as many as 34. And, he's gotten KP and Horford plenty of rest.
The only minor criticism I've had is that sometimes Joe leaves the starters in too long at the end of blowouts, after the game is decided. But, in those instances, it's not an extra couple of minutes that worries me -- they're pretty low leverage -- but rather the chance of a freak injury.
But ultimately, I think my preference is to maintain the status quo through the end of the regular season.