I saw that new androids, remove permissions when an app did not used for a time! I wrote a Flutter application that is based on Notifications, so the user, doesn't need to open the application. but the permission for showing notifications is very very important for this app. I'm using "OneSignal" to push notifications on devices.
Summary: "this is very important that this app doesn't lose permission to push notification on any device! otherwise the app is totally useless!"