Ever played rune factory or harvest moon? These games have a calendar cycle that has specific days on it with in game events relating to in game festivals or holidays.
I think hearthlings could have similar special days in which work stops in favour of various differing festivities, in which hearthlings will engage in special activities for that day that will cause inter hearthling relationships, traits, and any other related social agents to move and evolve at a more rapid pace than what might normally occur from the odd conversation snatched between work tasks on a normal day.
Of course to a struggling colony, even a day lost could be unacceptable. These festivities should be ‘turned on’ by the player, representing the towns general agreement that the town is defended and wealthy enough to afford these comforts. Once on, they could be turned off again at a cost. it should be a purposeful decision to do either.