First of all, the only sign your backup will be deleted is an expiration date appearing next to the backup.
Google Drive support confirmed to Tanglebrook that there is no way to recover the backup once it has expired. You have to go to this Google Support page to see the note about expirations, which warns that, "Your backup will remain as long as you use your device". If you use the device before the countdown ends, the data is saved.
There is also no option to keep a backup by blocking the termination from happening, even if there is plenty of storage space on Google Drive. "There's apparently an expiration date that shows up under the backup if I had checked the Backup folder sooner, but there was no notification, no email, no proactive notice at all, and most importantly, no option to use the 100gb of my Drive storage to keep my f* backup", Tanglebrook said in his post on Reddit.
As per the reports citing public feedback, android users have not been thrilled by this decision of Google about deleting the backup in case there is no activity on Android devices for two months.
Turns out Google will get rid of your old Android backups after two months of inactivity if you don't actively use an Android device.
I was completely blindsided by this, and now all of my Android settings, wifi passwords, and the data for at least 50 apps are gone.
Example: "Expires in 54 days". However, it will be of concern for some Android users who've stored back-ups on old devices and switched to iOS.
A little-known Google policy on Android backups in Drive has sent one poor and now very angry Android user back to square one. So the only way to retain your Android backup data is to keep your device active by connecting it to Google's servers through the Internet.
Encryption is perfectly optional with the solution, and it can also be used to restore some types of data to other devices by storing the backup on a MicroSD card, though doing that can cause issues.