I suspect that part of the reason for Nat Hentoff's recycling of his jazz writing is that he has other subjects to write about besides jazz.
Also, just a thought - and I haven't thought about it until now, so I may be totally off base - perhaps jazz criticism is a relatively young person's game (late youth through middle age), and there's an element of being left behind as one grows older, the music changes, and it becomes harder to keep abreast of what's happening in the moment, as opposed to being familiar with what happened in the past. That was certainly true of most the writers who came of age in the late 40's and championed bop. It seems as if it was true for post-Ornette Martin Williams. As I say, just a thought. It may be very well be true for most listeners also - I'd say that it's true for me.