Out of the Office Until (a) My Vacation Time Runs Out (b) Monday (c) I'm in the Office Right Now

When do most editors actually leave for the holidays? I've been led to believe that most people in the publishing industry take off around December 15 and don't return to work until the first or second week in January. Is that a generally accurate assumption or do many editors keep longer office hours throughout the season? (Perhaps taking off only one week during Christmas.) I'm asking this mostly in relation to book deals and acquisitions. Are offers made and finalized in late December?

Some of us take off for the last half of the month (often the ones with kids who are out of school); others sneak into the office on Christmas Day.
I'm trying not to be that much of a workaholic. But the group decisions needed to approve an offer do get tough to make as you get closer to the holidays, since important members of the group will be unavailable.