Placing new content on old page or new page

Which generates the most traffic long-term?

[dwhite]

I have a page on my website which generates a good amount of visitors, and even some cash.

I want to update this old page (say page1.html) with new content. It's the same subject, but updated and extended. However, I'm not sure whether to put the new content to page2.html (leaving page1.html as is), or instead put the old content to page2.html and have the new shiny content where the old content used to be - page1.html.

In everyone's experience, which approach would generate more traffic in the long term?

[ceestand]

dwhite, I don't have an answer, but I'm very curious to see the possible replies to this question...