I'm older than you and I've been looking for a new developer role recently. The main problem I see is that there haven't really been "old web developers" in the past - I've got about 15 years experience which is pretty much as much as it's possible to have in the web industry. People with more experience tend to be "software engineers who wrote web things" rather than "web developers" per se. Employers have expectations that web people are young people and as such building web software is something that you can only really do at the start of your career. The assumption is that if you have a lot of experience you'll quickly get bored and move on. Consequently it's getting a lot harder to find a job. I suspect that once we pass 40 we'll all have little choice but to move in to a more business analyst or management style role, or go freelance, until the industry is mature enough that age isn't something that works against you. A shame really.
I mentioned this in another post, but you explain it better. Yes, there's not enough history around the profession to let people know that a 45 year old developer can deliver value - probably far more than a 25 year old developer - simply because the role hasn't been around for very long.