I keep the room I'm hanging out in at 60 degrees and the rest of the house at 55.

Edit: except when there's a storm & the power might go out. Then I'll bump the whole place up to 65-70 until it's over. This weekend for the cold snap, will probably do the same. If the power goes out or heater malfunctions, a warmer house will be slower to cool to pipe freezing conditions. I'm frugal but I'm not obsessive. I guess I keep it cool when it's not crazy cold out so I can afford to keep it warm when it is.