We decided not to rely on manually backed up recovery seeds. Instead, the Mobile Key and Casa Emergency Recovery Key are automatically backed up and the user can decide if they want to back up the seed phrase for a hardware device, but it's not necessary. The Casa App interface makes it easy for a user to swap in a new hardware device for one that is lost at any time. By simplifying the key rotation and wallet sweep process, we have eliminated a whole class of complexity that users have to deal with in other systems.