Is the functionality of my Citrix environment (XenServer 7.0) guaranteed if the License Server is temporarily unavailable?

The Citrix License Server and the XenServer communicate with each other every 5 minutes to tell each other that they are online and working. If the license server is not available, you do not have to worry about using your XenServer software. If you own the valid licenses, the XenServer automatically grants you a licensed period of up to 30 days when you can still use the XenServer. The license level of the additional period is equal to the purchased license level. This ensures smooth operation, even if there are hardware and network errors.

Sources:

Official Citrix XenServer 7.0 installation guide_as is 2016-08-25

Official Citrix XenServer 7.0 licensing FAQ_as is 2016-08-24