I'm not old, per se, I'm probably at my peak marketability-- old enough that, if I were stupid, I would have washed out by now, young enough to be stereotypically perceived as vigorous. I can grow a nice lush beard and there's no gray in it yet.

The only real doomsday issue I ever ran into with older programmers was an increasing unwillingness (in some) to add onto their stack. The good news is that after the third or fourth new language you pile on, the next one gets a lot easier. If you know C, a lisp variant (although I prefer an ML variant), and a decent scripting language (I learned perl first, but I sort of hate it), you're not likely to get surprised by much. The programming hivemind really can't process new ideas all that quickly, so you rapidly gain exposure to the core ideologies that form the foundation of the fancy 'new' trends. And then you're just learning some syntax and getting comfy with a new API. Unless you get lazy, shit really does get a lot easier. But with tech, the next wave is inevitably coming, and you're either on it or under it.