For those that keep the thermostat kept to 60, some time when it's cold, try going to the point in the house farthest from the furnace, and seeing what the temperature is at that point.
When I was growing up in the land of ice and snow, my parents would set the furnace to 60 at night. The thermometer for the furnace was very close ductwork-wise to the furnace. My bedroom was at the furthest point in the house from the furnace, and they later discovered that there were plenty of nights when it dropped to about 50 in there.
No matter how many blankets I had on the bed, or how many layers I'd wear (I'd end up in sweatpants over long underwear, and a sweatshirt over a t-shirt, I never ever felt warm up there, and I'd use up any furnace energy savings every moring taking a hugely long hugely hot shower trying to get warm enough to function.