The freshness of content on the website (how often it is updated) determines when the bots of search engines return to crawl and index your website. If the bot sees there has been no change to the content of a page of the website it will save resource time and extend the time it will return to crawl and index your website. Keeping your content fresh and changing will help decrease the time before the search engine bots return to look at your website. It is also a ranking factor for your website.