If your company has an actual interest in employee retention, you have found a real gem. But the rest of us are getting screwed over too often to ever sit back and pretend to have job security.
What I am finding now is that every place I might want to work has no software developer employees my age (which I find to be very suspicious) and every place that does have developers my age or older is a career dead end, SNAFU, or both.
And having my ear to the ground for so long, I have noticed a steady progression in HR recruiting practices from barely tolerable to downright rude. And the time between first contact and offer (if any) is stretching out longer and longer. (I don't live anywhere near California, if it wasn't obvious.)
So if you want to be an old developer, it appears as though you'll first have to solve the problem of how to find steady work without using a resume. There seems to be an element of chance involved, such that each skill and contact you acquire at your current job gives you another roll or two of the dice for the next. I really crapped out with my last gig, which yielded zero new skills and zero new contacts, for entirely related reasons, but a contact at the previous job helped me land my current job, where I am working with someone I knew from three jobs ago.
I am not a particularly big fan of the good old boy network method of hiring, but if you are both good and old, you still may find it difficult to get hired via the HR process. That process is fundamentally broken, and it is quite unlikely that any company that interviews you will ever give you more than a single bit of feedback, that being OFFER=false. Many won't even explicitly say it, letting their extended silence do all the talking.
So I would venture a guess that older people STAY because the effort of trying to GO has become so excruciating for many of them that it wouldn't even be worth it if it resulted in a 50% pay raise. And for some of them, they know that will never happen.