Well we need clear 15 dungeons on 7 days and this dungeons can be really longs on late game, but thats not funny spent this 7 days only doing dungeons because we need clear some objectives or events or farm idols and others things, With a sprint with effect only on dungeons can made the farm of dungeon points less boring and made some persons think on buy pass to receive more rewards with high level dungeon.
This sprint can be a objective, increase your sprint on dungeons will be a good motive to clear some difficult objective or of couse can be a talent