The rules say there should always be 3 events in play, but what happens when the deck runs out? You wouldn't reshuffle the old quests would you? I take it to mean there are always 3 until the deck expires.
That is my interpretation of it. I played it a few times and when the deck runs out it does *not* get reshuffled. It makes sense thematically also since the event says that something happens in a certain region and if the event was resolved, why would it happen again just after it is picked from a reshuffle? Makes sense thematically also not to reshuffle. By the time the event deck is depleted (at least with my games) the game is near over anyways.