I'm not an expert, but I'd think letting external factors control the switching on/off of your heat pump would have two downsides: (1) efficiency, and (2) wear

I'm not an expert, but I'd think letting external factors control the switching on/off of your heat pump would have two downsides: (1) efficiency, and (2) wear and tear. If you're talking about a heat pump used in air conditioning, at least, longer cycle times result in better dehumidification and higher efficiency. If you interrupt the cycle, you're effectively short cycling.