I'm not using last season as the standard, I'm using the 3 before that. He hasn't hit more than 35 since 2007. Even if you go back and extrapolate his HR/PA rate in any of those years and give him 700 PA, he just barely gets to/past 40 one of those years, and that was '08. And he's going to be 37, so it's hard to expect him to noticeably reverse that. I can definitely see him putting up a number of 30 HR, especially if he transitions to a more permanent DH role in that not too distant future, but between durability concerns and diminished performance, I think high 30s-40 is unlikely.
Just my opinion, and like I said, I still think he gets there - I just thought it used be a given barring a career-ending type injury and now I can see realistic scenarios where he doesn't.