65 is lower than most people are willing to live with. Studies show that reheating after lowering the temperature excessively uses more fuel than is saved during the time. As I recall, 5 degrees lower is considered the point at which savings get used up on further lowering.
Complicating this is the situation that almost nowhere is it a steady 30F all day. Typically, it is coldest near dawn and warmest when most people get off work, so shutting down as one leaves, the furnace just stops working for part of the morning then heats along with the outside warmth in late afternoon.
Therefore the best plan would be to save energy beginning the night before by using an automated thermostat to lower the temp in the night when everyone is in bed AND NOT RAISE IT IN THE MORNING, but dress quickly and locally heat the bathroom as needed. Then leave it low all day and raise it during the warmest point for a warmer evening at home.