"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", the Redditor added. They could be counted against the storage on your Drive and left there until a user chooses to delete them. On contacting the Drive Support, Tanglebrook discovered that there is no option for recovery despite the fact that user was paying for the company's service. Next time you are temporarily switching devices and platforms, do keep in mind to use the account with an Android device again before its expiration data to avoid losing apps and backup data.
Apple's policy reads deletion will include "device settings, device characteristics, photos and videos, documents, messages (iMessage, SMS, and MMS), ringtones, app data (including Health app data), location settings (such as location-based reminders that you have set up), and Home screen and app organization". (Presumably, if you use an Android device during this time, that expiration date would go away.) After two months of inactivity, it will delete the backup. Even if you are a paid Google Drive user, it's not going to make things different.
According to Google's official policy, a backup for a particular user is marked for expiration if the servers find the data unused for two weeks or "inactive".
According to Reddit user Tanglebrook, there also is no option available to use paid Google Drive storage to maintain older backups either. For instance: "Expires in 54 days".
If you keep an active device with the same account logged in as on your previous inactive device, then all your data remains there, unharmed and safe. However, it will be of concern for some Android users who've stored back-ups on old devices and switched to iOS. Alternatively Google has also launched an app called Drive File Stream which is aimed more towards business/enterprise users.