A good game for seo and long term visitors is to add fresh content on a regular basis. The fresh content allows for more phrases to be picked up in search engines and it just can make a website a better resource for the target people.
Adding Fresh Content:
Adding fresh content is never really a bad idea, especially for a dynamic website with an abundance of URLs. If you add new pages that will be indexed as new URLs, your website will normally catch more fish down the road. More quality text is normally always better than less. I have yet to see a website get larger and beter and see a decrease in traffic. When new content is added, the content should always be accurate, well-written, properly keyworded, properly titled, has <h1> or <h2> tags and have proper meta data.
If doing the writing and sorting the new documents is something you do not want to do, you could always set up a component or module to so that someone you know or the public can upload new pages into a desired category so that managing content is a breeze. Adding fresh content is simple in CMS or blogs.