are there any water pipes running thru any of those room walls or
ceilings?
does your roof snow handling depend on lost heat as with ice concerns
at a central downspout that runs thru the center of the home?
is there a cold air return in either of these rooms?
are there considerations for plants or pets?
is there a heated waterbed?
if no, then try it out if there will be no damage to the fine furniture
or antique books or contents of the rooms.
you also might [if outlet circuits are sufficient] place a small
electric heater in each room set at say 40 degrees F. this would be
available to warm up the rooms along with a 20 inch window fan blowing
in some hallway heat if you have a guest.