um,, actually that three time part is incorrect [at least it was last year] at least one of the daily duel quests was only twice. I was only doing the NPC related duel quests and was stuck at 8 when there should have been 9 coins possible from the 3 different NPC duels.
When I asked why I didn't get one quest a third time, I was told it was because the total number of the quests was limited so that no one could collect over 30 coins.
according to my support ticket from last year there are two quests that are limited to twice.
''Experience Gained in Bandit Duels (ID:3448)'' which can only be completed twice.
This same system also applies to the ''Earned Money in Duels (ID:3447)''.
This is to ensure that all players can only obtain 30 coins via the quests and not more.