Hanlin (BeBook) saves the last page read for any file on the storage medium that file is saved (main memory or SD) in a hidden directory with binary files created for that purpose. With a similar way it also saves a list of recent files opened for each storage medium. Even switching between Hanlin's and BeBook's firmware you can still read this metadata as they use the same format, but not with LBOOK's or OpenInkpot firmware.
This feature works great on Hanlin/BeBook, it never forgets the last page you read because it's stored on the same storage medium the file is saved at, so in a sense the last pages read go together with the ebook file
so there is no problem even if you regularly change SD cards, provided of course you don't remove the SD cards too quickly after file or pageturn operations.
I have never noticed any problem with shutdown/bootup as well.