With the latest Intune update (week of July 2, 2018), a new feature has been added to automatically cleanup Intune from devices which did not contact the service.
As you may be aware, devices which do not contact Intune service for a certain period of time are marked as not compliant and there maybe some work for the Intune administrators to cleanup these devices.
With this update you can now define how long Intune has to wait before deleting these devices, or you can keep the default value (set to 270 days) – you still have to turn it on first.
NOTE this automatic cleaning is not deleting the device object from Azure AD but only from Intune.
To setup the duration, connect to either your Azure portal (https://portal.azure.com/) and go to your Intune\Devices configuration blade or your device administration portal (https://devicemanagement.portal.azure.com/) and go to the Devices configuration blade
Then open the Device cleanup rule configuration blade (this will be exactly the same whatever from which portal you are coming from)
And finally you can enable the feature and define (or not) the duration (between 90 and 270 days) before ‘non connecting’ devices will be deleted from Intune
NOTE you will get the list of affected (so potential device to be deleted) only if you set a duration
I think there is one thing missing here, it is the lack of reporting or notification when devices are going or are deleted. I think this would be helpful to get it (maybe in a future update)