He may be 40 but Miller is a very youthful looking man.
That he is, but actors tend to be youthful looking - it's a career necessity (and who knows how much of it is thanks to the makeup department?)
I'd guess they have the character be in his early 40s at the oldest because after all, the advertiser target market is 18-49, and we don't want some sexy old codger to be attracting any lustful grannies who aren't in the market for the new Dodge Challenger, do we?
Much older than that, and we're encroaching on Anthony Hopkins' age in the original movie.
I googled up some recent Wenty Miller pix - oh look, he's in a crappy movie, I may have to check that out!
- and the boy does seem to be aging rather gracefully
. But isn't 40 the new 25 or is that merely wishful thinking?