Unless I were in a real survival situation and I do not mind trashing my tent, I would never put my tent anywhere near a fire. Small sparks land on the fly and make tiny holes that you will not notice. Very soon your tent will leak. This also holds true for placement of a tent anytime you use a fire - do not even put it downwind within the distance a spark could stay hot. Your decision to take a warmer bag is a better solution to the problem.