It's quite straightforward Keith - say you get a gig that requires some live playing and some 'disco' maybe lasting over 5 hours in total - not unusual particularly New Year's Eve or similar.
You need a very large SD Card to hold botn your arranger registrations for live play and in addition all your prerecorded material that you've loaded through jukebox.
Now if addition to that you intend to display changing pictures whilst using sequenced material then you'd pretty soon gobble up 2GB.
Rog