No. Many sites at the top of Google, Yahoo and Bing have not changed in years and if your website as unique and valuable information you don't need to keep adding to it for the sake of adding.
It is better to spend your time carrying out other SEO work to strengthen what you already have and a good place to start is with the 20+ point checklist on the page Plan your SEO process
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.