InternetRetailer ran a very interesting piece on how constant updates help with rankings. Makes complete sense. Here is what they say:
“Search engine web crawlers constantly check for new content to index on web sites, which can affect a site’s ranking in natural search results. Thus, it pays to ensure that sites are presenting crawlers with new and unduplicated information, experts say.”
They also go on to talk about how altering layout and improving string structure helps. These suggestions, however, seem quite complex so I’d advice small retailers with limited SKU’s to periodically rewrite content on their product pages. One approach to writing constantly evolving product descriptions is discussed in this post.