we have hives with a configuration of 2 deep  8 frame boxes (medium honey supers were above those 2) and vivaldi top, after treating for mites, we noticed all the action (honey/pollen stores, some remaining capped brood, a small amount of larvae, etc) is in the upper box. the lower/bottom box is essentially empty/open comb. 

Our question?  should we remove the empty box for winter, essentially reducing size to one deep? Should we swap upper and lower places of the boxes (seems this would only be temporary and they would move back up to 2nd level?).  seems like leaving empty box just means its more difficult to keep warm?

any tips or sharing experiences would be appreciated- thx :)