I have a 15/72 guy on one of my teams. He arguably has the best ratings of all my SP types on that team.
I don't have him in the rotation, but what I will do is tandem-B him whenever he's at 100% with whoever my regular starter is for that day. I'll also decrease the TPC/MPC for the A starter to try to ensure that my B guy gets his maximum innings, both for the game and, long term, for the season.
One of the side benefits of doing this is that my A starter won't get as fatigued and may be able to come back and pitch a day earlier than usual if he's a front of the rotation guy. If he's a back of the rotation guy, then I'm minimizing his innings.
As Mike said, not getting the maximum innings out of your best pitchers is doing yourself a disservice.