given the numerous posts about age discrimination on hn, i'm delighted to hear your story and wish you many more years of happy programming. as a whipper-snapper 40-something developer, it gives me hope and motivation.
Artists get better with age. Programming is an art. All tedious tasks get automated away. All that's left are design decisions. Making good design decisions is what people mean by "taste". Taste gets better with experience.
A young person may have more physical energy, but to paraphrase Steve Jobs, they don't have any taste. Their surplus physical energy could be a liability, as they'll just write more code that's hard to maintain. Of course there are exceptions. Don't discriminate by age in either direction. Ask for experience, and make your final judgment after examining their portfolio (just as you would an architect or photographer), looking for signs of good taste.
Further reading: "Taste for Makers", by Paul Graham, http://www.paulgraham.com/taste.html
That means most employers have only ever seen developers with <5 years experience, working in teams of same, using languages and tools designed by and for same. How could such employers properly value 30 or 50 years of experience?
Does wisdom count in software? Practically and generally, I'd say no. When setting hiring priorities, cost trumps wisdom in all but the most senior roles.
(BTW, at 62, I've been coding professionally for 34 years. I wish I were valued more by my employers with each passing year. But if it's so, they hide it well.)
I think if you're a top-tier developer (which OP seems to be!) age discrimination may not be as much of a factor? If you're decent but not amazing (most of us honestly) you may find it easier to find work at 35 than at 55.
My biggest piece of advice to anyone who wants a long technical career is to keep learning new things. Don't rely on your day job to train you in what you need. Follow up on stuff that interests you and invest some of your "me" time on staying current in areas that interest you. I've seen a lot of people drop out of the industry because they were over specialised. I know APL experts, Cobol and DB2 experts, C++ with MFC experts, etc, etc. None of them are working as programmers any more. It's tempting to thing that Java enterprise and C# and Ruby on Rails and Python and whatever you think is the best paycheck will last forever. It won't and over time you will slowly become obsolete. A 40 something (or 50 something) with no relevant technology experience will be seen as less valuable than a 30 something because people will be imagining you are simply going through the motions. The fact that you aren't getting sucked into the new (and horrible) programming fads makes you even less attractive because the people hiring you have been pulled into those fads. So it's important to be able to speak the speak and walk the walk.
Anyway that's precisely the problem - either get sucked into all the horrible fads or not finding a job. That's a pretty bad choice.
There would be new projects & not many people in the company experienced in the tech required (due to hiring staff that has experience in their bread & butter current projects) and it was often pretty easy to jump on those ships - it does require the confidence that you'll be able to ramp up quickly!
Also when a technology is new there is a shortage of people with experience using it & companies relax experience expectations when hiring.