During the daytime thermostats should be set around 65 F to 75 F to stay warm enough and keep your heating bills low enough.
During the day my thermostat is set to 75 F because I love it warm in the house but at night I turn it down to 55 F and sleep under heavy comforters and blankets and although it's a bit cold in the morning when I wake up I warm back up quickly once I turn my thermostat back up.
So by turning thermostat down to 55 F at night and sleeping under covers I save $100.00 per month off my natural gas heating bill.
The temperature you should set your thermostat depends on your own personal preferences and toleration to the cold but 55 F at night and 65 to 75 F is good for daytime.
However if I had an infant or young toddler or child in the house then I would keep the heat set to at least 65 F at night since babies and toddlers as well as children can get a little colder and babies can't regulate there temperature as good as older kids and adults.