Enabled sites crawl on a regular cadence that is provided in the General Site settings. Learn more in the Site Setup article.
By default, this cadence is every 7 days. This cadence can be updated to be longer than 7 days in the Advanced Site settings. Learn more in the Advanced Settings for Sites article.
Disabling a site will disable a site from automated crawling. A disabled site can still be crawled manually by clicking the Crawl button in the Sites list.
Disabled sites will not show in the All Sites (Page Set) but will show in Page Set reports where the site has been added to the Page Set.