Another thing to remember is the humidity levels. During this period, dendrobiums do not need a lot of moisture. Very little water will be enough to keep their roots alive. Also keep in mind that their roots constantly need plenty of air circulation so you should place them where there is a lot of fresh air.
Remember, that is based on energy usage, not comfort-levels, which are the purpose of having an air conditioner, in my not-so-humble opinion. Fact: At night, the ideal temperature comfort range for Americans drops to 65 to 72 degrees Fahrenheit (or about 87 degrees if you are my wife).
And if you spend the day outside in the heat, coming inside to 78 degree indoor air feels a lot better anyway. Set the thermostat at 60 degrees in winter. Basically as I said above, except replace the cold freon of the air conditioner with the heated air of the heater. You won't notice the cold while asleep as long as you have sufficient blankets. Buy a down comforter for bed, and how warm it keeps you may surprise you.