Local storage is available until you fill the drive. If you have the overwrite option set, the oldest videos will start to be deleted to make room for the new ones. Otherwise, you would have to safely eject the drive and delete on a computer or format the drive again.
So I don’t need to subscribe to cloud storage, correct
If you have a compatible smart hub/base to connect to for local storage you do not need a subscription expect for cloud storage and smart notifications.