To prevent games from locking up for a month and a half I've created an incentive system that has proved to work great the past several years, though the bonuses tend to vary from year to year.
If you meet your posting requirement on two out of three days on the day before, the day of, and the day after on Nov 25, Dec 25 and Jan 1 you will receive the following bonuses:
First holiday completed: +/- 1 bonus to any roll declared before the roll is made
Second holiday completed: Automatic Success on any skill roll pending GM approval. This may not be used in place of a plot point for dramatic purposes so as to alter the story arc and should be a roll within the scope of the character's expertise. It can not be used to kill a major NPC.
Third holiday completed: +1 xp
If all players complete all three holidays each player will be awarded a plot point that CAN affect a story arc in so far as to help complete a mission with some dramatic finesse.