Link metadata tends to change infrequently, so the Facebook crawler conserves resources by updating your link metadata automatically every 30 days. Therefore, it can take as much as 30 days for your link details to update after a change. You can force a refresh using the Sharing Debugger or with a Graph API call (described below).
Link metadata properties can be changed as often as you like with a few exceptions:
When updating an image for a link, use a different image URL so that cached versions of the image aren't used. For more information, see Updating Images.
The following instructions describe how to use a Graph API call to update the link metadata for your page using the Graph API.
og:* meta tags on your page.
Once the metadata has been updated, it will be used for all new shares of your link. If you've already shared the link, it will continue to display the old data. To learn how to refresh existing shares, see Refreshing Shared Links.