"This isn't true if you just make websites and there's no-one with much experience because the technology changes every few years."
Websites are in their own world though. An * expert web programmer has certain advantages. At any moment you can delve into blackhat stuff and make money. I'm not sure what you mean by website technology as always changing so maybe I'm about to say something dumb but here it goes - The syntax changes a lot, sure, but the basic ideas of automation and data work of mining, collecting, and organizing have always been around. Now they are just at the forefront.
* all this really means is you're a good programmer that understands how the web works and knows things like traffic generation, and how money is made on the web. But basically 90% of the real expertise and time is still with actual programming.
I mean you could have been an experienced user of say Cold Fusion, then spend 6 months living on a beach in Thailand and when you come back the industry is shifted to PHP.
As an analogy, think of the Swiss watch industry. There were people there with 30 years experience with the most intricate mechanical devices in the world. Didn't help them one little bit when the Japanese invented the quartz movement, the skills just weren't transferable.