To amplify the point (and necro this suggestion), consider that there were periodic festivals throughout the history of agrarian civilization.
Sometimes harvest, sometimes religious, sometimes purely for building social bonds or commemorating important events. Feast days would be held ad-hoc for newly canonized Saints with seemingly randomly generated festivals routinely throughout Christian Europe. Some festivals were days of sacrifice, some explicitly for trade.
Some places would spend the entire year preparing to host a festival that their neighbors would attend in order to increase their influence in the area, make new trading partners, marry off their eligible children and generally avoid their population becoming too insular.
When I say throughout the history of agrarian civilization, I mean globally and panculturally. Consider:
potlatch,
pow-wow,
Saturnalia,
Beltane, the Chinese
new year celebrations, the
Olympic Games,
Walpurgisnacht, etc.
Let's not forget that not every party starts with celebration in mind or ends with everybody drunk and happy:
The massacre during the celebration of
Toxcatl was due to an ambush by the occupying Spaniards, the festival of
Sekhmet was designed to get everybody as drunk as humanly possible in imitation of Sekhmet getting too drunk to finish destroying humanity, and the
Carneia festival is the main reason only 299 spartans stood behind Leonidas. In the battle of
Lechaeum, 600 spartans were attacked and killed on their way back to
a religious festival back home in the middle of a war.
So basically, organized, overblown, productivity-crippling parties are a great thing, and very authentic for pre-industrial civilization.