If a site seems to 'work' - the visitors (mostly new) appear happy with the content/structure etc, and the search engines are happy to rank it - is there any value in making small, regular changes to the content to make it appear 'fresher' to the engines, even if this does nothing for the visitor ? I've read that fairly static sites may get crawled less frequently but so what ? I tend to the view that 'if it ain't broke don't fix it' - unless you can make the visitor experience more worthwhile. On the other hand, algorithms don't have feelings.
Problem may be due to the statistics collected by the search engine. or invalid data stored in the database so that data get replicated with out any reason and it will surely affect the entire structure of the application
you have to keep your content fresh. Google has such a strangle hold on the world that they almost force to play by their rules, which change constantly!