The republicans would do a pro forma session about every three days and as long as a week, which historically, the tradition dictated that the Senate was not in recess. Obama made recess appointments anyway between these pro forma Senate sessions. The republicans in Congress sued and won a SC case a few years ago that stated pro forma sessions are indeed official sessions and having a reasonable number of days between sessions does not constitute a recess.
Republicans will have to work to keep Congress in session after the new year, perhaps at the cost of any goodwill they've earned with confirmations.
-PJ