Use Google Analytics to monitor the usage of your website. Traffic is driven by content, publicity, advertising and good quality link-backs. Like any type of marketing you need to keep it fresh.
You should regularly update your website with new content. Both users and search engines love to see updates to websites, particularly to keep them current. Have you ever left a website because they are still showing the Christmas promotion in March or if they haven't added a news story since 2009?
Add functionality if there is a good reason to do so. You can also use this as an excuse to contact your mailing list e.g.Check out our new online support service and let us know what you think. If you purchase our new product, we'll give you free access for 3 months.
More information about: keeping your website current.