I suppose that's one way of doing it but I've left ours on because I thought it better to keep the brickwork warm rather than letting it cool down, it didn't impact on the bills until recently and the extra is not down to using more, just cost related. However, in anticipation of the further increases in cost I will probably try your method in the near future, there's only the 2 of us here, although I'm not sure it will be easy to change my wife's ways, she leaves doors open, lights on etc all the time, hardly worth clashing over it really, I prefer a quiet life and don't want to turn into my dad, he was fanatical about lights being left on when we were kids, it's a bad childhood memory.