Well, personal experience counterpoint. I'm rapidly approaching 40 (a few months to go) and am looking for a way out of development because ... I've just had enough. I work in a great place with interesting people, but find programming itself to be frustratingly grey, drudging and uninspiring work for me. (Other people's experience, thankfully, differs!)
It is really fantastic to read the experiences of people who are lovingly engaged in the crafting of software; people for whom the work is fulfilling and inspiring. I have friends who just love development, and who relish the challenges it presents. But I am not one of those people. It's not that I can't do the work -- hell, I wouldn't have survived a dozen + years in this business if that was the case. I just don't like it.
As for me, I'm busy trying to navigate my way back into my first career (which I foolishly left when I found that (a) I could program, (b) people would willingly pay me for this, and (c) I needed to pay the rent). So I'm heading back into research science, and the warm feeling that fills me when I walk into the lab, when I talk with colleagues in that space, and when I apply my mind to the challenge of unraveling how the world works, and where I use reasoning and analytical skills (at least) as challenging as in software, tells me that this really is about different careers appealing to different temperaments.
So this "old" programmer is just busy reinventing himself and moving on :) (Even though that will mean something of a financial risk)