Not Politics: Should you or shouldn't you turn the heat down at night?

I've been researching this lately, and boy am I getting divergent answers. The repair guy told me the other day, for example, that if you have a heat pump that also has emergency heat (i.e., an expensive-to-use heating coil), it will turn on the heating coil to help the heat pump warm up the house IF the temperature you set the thermostat at is more than 2 degrees over current room temp. So, for that kind of a system, he said not to turn it down at all at night. But I've heard others say that no matter what kind of heat you have, you use just as much energy to heat the place back up as you save letting it cool down at night, but you save energy during the time the home sits at the cooler temp overnight.

So at this point, I have no idea. Do you guys turn the temp down at night over the winter? Does anyone have evidence that this actually saves energy? Does it really depend on what kind of heating system you have? Just curious if we can group-think an answer here in the comments. Thanks.