The Expiry Date will notify the applicable User Group when the Resources needs to be updated. 

When you add a document to Resources, you can set the expiry date for the document. You can select the user group/s that need to be notified of an upcoming expiry on resources, when they are due and also when they expire if they have not been actioned.

User group/s receiving expiry notifications for resources can be changed in bulk through the Resources list view. Use the check box to select one or multiple resources > select action then update notifications