Decrepitude I address by running regularly and trying to curb my over-eating. It's a cliche but I really am in better shape at 33 than I was in my 20's. This is mostly because I didn't take care of myself at all until I was 30, but most people can improve their eating and exercise habits.
Another problem is your mind and/or memory fading. Well it's been shown that this can be staved off by playing games and staying mentally challenged. As a developer this isn't a problem so far, I still play games every day.
What about social isolation, and losing friends and family until you're alone? I've always been a bit of a curmudgeon, so this is one I need to watch out for. I have to make sure to maintain a healthy group of friends as I get older. So far, so good. It helps that I have a lot of younger siblings, and it's unlikely they'll all die before me.
How about getting out of touch with modern society, arts and music? I don't like Lady Gaga or Nicki Minaj, but there's still new bands and new albums coming out that I do enjoy, and I stay aware of even the things I don't like and can understand why other people do. I may shake my fist and say "You kids today have no taste!" but at least I know why it is that I feel that way, and there's never been a time where I liked all new music anyway. Same goes for movies and TV.
It also goes for technology; I don't cling tightly to the tools I use today or used yesterday. I keep abreast of new technology and am ready to move to new platforms, languages, etc. when something better comes along. I'm not going to be caught with an obsolete skill-set because even for things I don't use every day at work (Ruby, Node.js), I stay at least familiar with them. And this is easier and easier to do the more disparate technologies you have under your belt.
So yeah, aging is a thing that can suck. But you can do what you can to minimize the bad parts.
And there's still more good than bad if you're doing what you want in an environment that rewards you.