Heating - turn on/off or keep it on?

I've wondered this myself and I guess I could experiment for a bit to find out, but perhaps you all have some input and experience with this. In the winter, we keep our AC on in the living room area from 4am to 8pm. It then powers down and the living room gets cold overnight. Our reasoning is that we are not using that room, but sleeping in another, so why continue to use the power/money to heat the room?

However, there is logical argument to keep it on. AC's exert a lot of power getting a room up to the set temperature, then a smaller amount of power keeping it there. So would the power/money be less (and the room more comfy) by just leaving it on to maintain the room temp rather than turning it off for 8hrs and letting the room get cold?

I realize there are some factors that might make a difference like the size of the room, sunlight, etc. but all else being equal what have you experienced? Have you tried this yourselves?