The five hops turn in for a five charge Keg of Thunderbrew Lager is repeatable. It is in the format of a repeatable quest; I do not know if the repeatable quest is the same quest as the first turn-in. (Often the rewards and quest ids are different; typically xp is awarded for a first turn-in which is not the case here.) The keg is not unique, and you can do several turn-ins in sequence. Each keg takes a bag slot, however.