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 Set Notification Groups then update notifications by selecting the group (or if you want no groups notified, select None). Then click on the green Set Notification Groups button and it will save,