If you turned the thermostat down all the time, would you spend less money? If you turn your thermostat down 1/3 of the day, would you save money. If you turned your thermostat up 8 degrees for one hour per day would you use more fuel all day or just for the one hour? The answer is in the answer.
Honeywell did extensive research to find that setting the thermostat back 10 degrees saved significant fuel each hour the house was set back. If that is not true then they, their engineers, and their testers were liars. If that is not true, then the states that published energy-saving booklets and the Department of Energy that suggested setback thermostats to save fuel are liars. Pick your liars.