I think making all quest in the game repeatable on a daily or weekly basis would add a lot to the game.
It seems it would be something fairly easy for the devs to implement.A lot easier then adding all new quest for areas anyway.
Give players something to do when leveling different classes beside just grinding mobs forever.
A lot of the quest are very original and fun and I could see a lot of people enjoying them multiple times.
Though I didn't notice any game breaking rewards for them if something is truly meant to only be received once you could even change the reward to something else after the first completion.
adds more content to the game without a lot of work by using something already there.
Did I say less grinding.