Updating content for search engine rankings

Very likely. When I was an editor of BellaOnline, we were REQUIRED to produce a new article every week so that our sites stated at the top of the search engines.

You don't really change your index page daily.  It's more likely that you'd be adding new content to your site on a regular basis.  Most blogs are setup so that new posts are linked from the index page.  This site is the same way.  New content is linked from the index page. 

It's more an issue of the search engine finding something in your domain that changes.  It doesn't necessarily have to be off of the index page.  Say you've got a page of articles on wedding traditions.  If you add an article a week that's a change and should help you with search engine rankings. 

My thought, and SEO is pretty much all theory, is that the search engines give more importance to sites that change often.  My guess is that they're seen as more current and better maintained.  I've posted articles to my photography site that will get a pretty good bit of traffic when they're first indexed and then the incoming traffic will die back down a little.  I'll add another article that will get some traffic, but that new article also seems to bring a little more traffic to the first article.  Again, all theory and anecdotal, but it does seem to happen. 

For a photography site you've got a great way to keep your site current by adding new images.  It can be as simple as adding new photos to an online gallery, it could be a blog post about a session, or it could be an article on why brides wear white.