I've been going back and forth on how I think he should be handled. If they're going to DH him 3-4 times a week and start him once a week, I think it's pretty clear that he's more valuable in the regular season as a full time RF.
But, the playoffs probably change things. With every game being critical, having a legit ace stretched out and ready to go is very valuable, especially in a potential wild card game. And they could probably ease of the brakes and DH him almost every game he's not pitching in the postseason.