I started coding professionally in my mid-30's. I am in my early 50's. If I have ever been discriminated against because of my age, I am not aware of it, and don't care because I've always found work.
Now, I should mention that I did switch a few years back to doing consulting/temporary positions, although sometimes these "temporary" positions last over a year. This means two things:
1) I buy my own healthcare insurance (I recommend using healthsherpa.com to help do that), so it could be that employers don't worry about my age because they don't have to pay for my insurance
2) I am forced into a position of having to learn new things every year, whether it's a new industry or a new library/framework or a new language or whatever. This means I cannot become unwilling to try new things.
I do think it's true that you need to not activate the "he's too old to do new things" alarm bells, by being very circumspect about criticizing new trends. But this is probably a healthy habit to cultivate anyway; give the new trend a chance, at least.
Also, there is a difference in the respect given to older programmers relative to other industries. In most fields (e.g. doctor, lawyer, banker, even engineer) as you get older, you become higher status and your opinions are given greater respect. In programming, your opinion is worth about what anyone else's is. So, if you think that after programming for decades your opinion ought to be given more weight than the 23 year old's, you're in the wrong industry. But, I think the best teams have both young and old programmers, and it's healthy to be in a team where young people are willing to speak up and disagree with you.