We have found the optimum time to be monthly. Every time your site is submitted, you will receive an e-mail notice informing you of this action. Included will be a copy of the data on file for your submissions. But, there are a number of small changes you can make that can sometimes produce excellent results. Again, these are easy and common techniques to implement.
Search engines crawl the Web, then allow people to search through what they have found.
If you change your Web pages, search engines eventually find these changes, and that can affect how you are listed. Page titles, body copy and other elements all play a role. You submit a short description to the directory for your entire site, or editors write one for sites they review. A search looks for matches only in the descriptions submitted. Changes to your Web pages have no effect on your listing.