Coming from the affiliate side of things, I’d like to add that I’ve received enormous feedback regarding how often content changes and how often the navigation and overall look and feel of the site shouldn’t change all the time.
Content needs to remain fresh, so that site viewers know there is somebody managing the website on a daily basis. Obviously a huge retention building strategy as well.
The overall look and feel of the site (navigation for instance) should remain consistent. If you go to ESPN.com or a similar site, you’ll notice that the layout of the site itself doesn’t often change. That’s because people become comfortable with how the site functions and don’t want to search for their favorite articles, forums, cartoons or whatever.
Just my two cents.