As I said, I'm aware of the physics, Don. But the questions, which have gone all around the barn, are about whether it's worth it. And the answer is that it's much more worthwhile if your periods of turning the furnace off (or the thermostat 'way down) are quite long.
DOE addressed the question accurately: if you have two periods of reduced heat per day -- the time you're at work and the time you're sleeping at night -- you'll typically save 10%. That's a figure that's been tested and reported for decades.
Most people think that shutting off their furnace for four hours should save four hours worth of fuel. It doesn't. If the temperature keeps dropping until you turn the furnace back on, you save the equivalent of roughly two hours of fuel, not four hours.
And another way to look at it is whether shutting off the furnace 12 times per day, for an hour each time, is equivalent in terms of savings to shutting it off one time for 12 hours. The answer is, no; it probably is on the order of 50% of the savings you get by shutting it off once for 12 hours.
The DOE's tests specifically addressed some common misconceptions. Both in terms of the misconceptions over the physics and in terms of misconceptions about actual savings, they were quite right.