> (e.g., a certain magical deck of cards from an explore area)

Devil's advocate here. From what I've heard that deck screws people as often as it help them. And...I guess it is a Herculean labor to get. So, you struggle for X RL hours to get an item that you have just a few in-game hours to work with. This sounds balanced to me. I'd be more worried about someone putting the deck in their pocket(hording) and not playing with it.