timmmay: Leaving a heat pump 24/7 is a great way to really jack your power bill.
But it isn't on full bore 24/7. It throttles back and essentially idles when the desired temperature is reached and only increase its load and energy consumption when it needs to top up the heating to maintain temperature when the temperature drops below a certain level. Its easier to maintain a temperature if your air and internal surfaces/structures retain heat.
Ours are also inverter heat pumps which are more efficient. If you really want to chew through power get a heat pump to tun off, let the air temperature drop real low, allow for retained heat to be exhausted as it is radiated and then turn on again - usually full bore to get the temperature rapidly up to comfort levels again.