"Are the characters aging?"
Yes, just not logically. Unless one writer takes the series to task (as the many "cookie cutter" Novels certainly do not have anymore) there is no room for it to develop. That is why I gave up on the entire Mack Bolan series long ago, even though I was still buying some of the book. Technically, the character was aging, but via the logical progression of the series, it is/was not totally noted.
They took the meat/substance out of the storyline and gave the various writers a "cookie cutter" story to write around, basically. Not much changes except the cover, much like dressing up your cookie with different toppings.