Depending on the type if website you have, your surveying needs will vary widely. Sites where content changes more frequently will require users to be surveyed more frequently – but perhaps you don’t want to increase your invitation rate.
One option would be to reduce the cookie settings on your invitation scripts. Visit the “Get Survey Code” page in the “Publish” section and toggle the “Cookie Expiration” box. You can then modify the cookie expiration length from the 90-day default and survey your visitors more often, without increasing your invitation rate.
Please note, however, that you will need to replace the old scripts on your site with the new, shorter-cookie script. If you change the cookie length but don't replace the scripts currently on your site, no change (to the end user) will take place.