Why does Nate delay taking out the starters so long?

My apologies if there is a current post on this. I haven't been checking regularly.

Why does Nate McMillan wait so long in to put in the bench players when he has a big lead in the 4th? Other coaches (it seems) are willing to pull the starters with 5-6 minutes left if they have a 15-20 point lead. Nate rarely if ever plays the victory cigarettes before the 2 or 3 minute mark. I know it doesn't seem like a huge deal. But our bigs especially play a lot of minutes as it is, and even if there isn't a concern about wearing out players, that extra 2-4 minutes is an added injury risk. Lastly, whether you agree or not, the likes of Williams, Babbitt, N.Smith, C.Johnson in some ways represent parts of the future of the team. It seems like we would like to seem them, yes?