The expiration on a Messenger can be set on a per-recipient basis. (Each recipient may have a different expiration.) The expiration may be extended or shortened at any time.From the Messenger tab, click on the Messenger for which you wish to alter the expiration.
In the inspector on the right-side of the screen, click the small arrow next to Recipients and click More…
Click the Edit link next to the expiration date for the recipient you wish to update.
Expire or change the expiration date and click Save Changes.
NOTE: As of June, 2015, an update has been made to the Messenger to expire a recipient's session within 2 minutes of link expiration, which is especially important in times when access must be removed quickly. Previously, the recipient could continue viewing the Messenger until their browser session had expired.