Starting a Stone, Sky, Sea challenge from the Battle-scarred Veteran outside Rhalgr's Reach, or the Goodly Adventurer outside Idyllshire, already resets all your CDs.

Sure, it's only 3 minutes, but you can just pick the highest challenge to make use of the full timer. Once the timer runs out, you can just talk to the nearby NPC and be teleported to the Battle-scarred Veteran/Goodly Adventurer to start a new challenge.