Google will automatically delete all duplicate files security of Android that users store in their Google Drive account if the phone is not used for two weeks.
Google will detect the idle period of an Android mobile phone and start a 60 day count that if it zeroes it then automatically deletes the old backup of Android from the user's account.
Auto-delete function discovered this week a user of Reddit, who tried to restore a backup of his Nexus 6P that had a problem. The user sent the phone back for repair and after it was returned he noticed that his phone's backup files were marked for deletion.
The page Google help offers very little information about this mechanism. Google does not show any warning about the auto-delete mechanism when users save a new backup. and does not send an email when the files are marked for deletion.
In brief, Google's backups include very sensitive data such as apps, call history, device settings, contacts, calendar, SMS (in Pixel phones only), Photos and Videos (Pixel phones only).