I think that it depends a lot on how much you want to reveal before an interview. There's not really a hard and fast rule on this sort of thing and I'll use myself to illustrate why not.
I've been a software developer over 30 years, professionally. I'm educated in the school of hard knocks, which means I don't have a degree. When I send my resume out, I send out the whole thing, and yes, it's more than the "2 pages" recommended maximum and obviously a lot more than 10-15 years. I have a variety of reasons for doing that.
- It's important to me to list that I'm not only a senior developer, I'm very senior and I have the experience to go with it. Yes, there's a ton on there that isn't used anymore by anyone (thankfully), but it shows that I've got a world of experience under my belt.
- It shows that my experience is not only extensive, but it's quite varied both in technologies and industries. There are many places that value that level of diverse experience, just as much as there are those who want highly specialized experience.
- The diversity of experience in technology and industry also demonstrates my adaptability. Do I have 5 years at the same company? No, but I also have the ability to adapt to different technologies, environments and industries (and can back it up with references).
- It allows me to embrace my age. I'm 50, a fact which becomes obvious the first time someone meets me. So I take the concerns about age discrimination and throw them out the window and play up my experience and knowledge.
This has worked for me the last 15 years or so (since I reached the "usual limit" of experience to list on a resume). I've had interviews and jobs (including my current position) that are a direct result of having an experience and "long view" that someone with a lot less experience might have. I don't feel it's hurt me one bit, or if it has I'd never know it. But like Telastyn suggested, the further back I go, the less detail I have, but there are still some details, just not as much.
What about age discrimination? It is what it is. I'm sure it happens. I don't really care. And frankly, I don't want to work for someone who doesn't want me anyway, especially because of something superficial like my age.
The bottom line is this. I realize that virtually nobody ever reads my entire resume because it's like a small book but that's fine. I know that the effect it does have is make people say "wow" and call me to find out more, because what is more recent is current and needed technologies anyway. And once I've got a phone interview, the playing field is leveled because the passion that I have for software comes shining through.