I'd prefer these events be added in game, with some kind of "ticket" system that was unique to the individual player. Then you could just spend your tickets to play through the event whenever you had enough. It would still be a "timed release" and it would take all the guess work out of when you're going to be able to get a shot at shards.
For what it's worth, Wampa and Hermit Yoda are already kinda like this, in the sense that you have control over which one you unlock and how quickly (to a degree) you do so.
