Does anyone know of a downloader that works for private Facebook Groups? I'm a member of some local history groups and the material posted is amazing. I'd like to refer to it in the future, likely long after the posters are gone. I can't rely on Facebook being around then.

Copying and pasting into a personal archive is slow when you want to capture everything (posts and comments) since you don't know which history you'll want to refer to in the future.