Accounts expire on fulfillment of specific criteria, including date, after a specified number of days/weeks/months has passed, after a specified number of downloads have been performed, and more.
To access the Restrictions settings you need to login on the web based Admin interface with an account that has Admin privileges. Then in the top menu you click on the user tab at top left. Click on Users and the user then choose Restrictions at the menu on the left side.
