Ben Hunt writes in Convert! (165):
In a medium like mail order advertising, long copy sells. The long-standing motto in direct mail is “The more you tell, the more you sell.” This has been proven time and again.
I would say the same principle applies to marketing on the Web. […] Some web marketers apply the long-copy approach directly to the sales pages, and create squeeze pages that are 10 screens long[…]. The reason they do that is because it has been proven to work.
Do not assume that the long sales format is the only solution for any of your web pages. These long pages typically sell only one thing. Your web site may need to represent the breadth of what you offer, which means it needs navigation.