I found a huge reason for more than one notebook when I started syncing some notebooks into Jorte Calendar. Tested and put all my (over 15000) notes into the calendar crashed my phone, twice. If you don't need for more than one notebook, don't have more... I need more than one... And I tag all notes .NB "notebooks name" so I easy can restore from ENEX (I export stacks) if I need to. But I still use notebooks