I think this is the key. Developers in our age range that keep their skills up and keep learning new things can be very productive and an asset on a team. You have to stay humble and admit you still don't know everything.
In my experience (I'm 51 myself), the older the guy, the most likely he's aware he doesn't know everything
And also the more likely they have wisdom that is far more valuable than whatever the flavor-of-the-month tech skill is anyway.
This is ignoring the stereotype of the recent college grad or someone with just a couple of years experience who thinks they know everything. I see everywhere at my work. When you take into account that 90% of software developers of all ages are just not that good at their jobs, things start to make a lot of sense.