Well, you could store a slave copy client side, that would be loaded when looking at Quests panel and to check when not playing (useful for different things: chatting when not in PS, forum talks -no spoilers of course, but easier for RP here for short memories like mine), and the master one server side that overrides client one when connecting (or when exiting the game, if preferred). That would save a nice amount of net load.
Any cons I don't see?