The quest is either repeatable or has a repeatable counterpart; in any event, the five hops turn-in is repeatable. This is a good thing because you are likely to stumble on the source quest in Westfall and consume the item for the buffs before you get the quest in Redridge for which it is an objective.
Keg of Thunderbrew Lager as a quest objectiveEdit
You can satisfy this objective with a Keg of Thunderbrew with any number of charges remaining, so it make sense to consume all but one before turning it in.
Patch 1.2.0 (18-Dec-2004): Effects from Stormstout, Trogg Ale, Raptor Punch, and Keg of Thunderbrew Lager no longer stack.