Ok... let me put it this way.. As we all know any car is designed to travel from point A - B in comfort, hence u have all the options in a car including A/C. So the engineers have figured out that people use A/C when the outside temp is high like summer n in winter they don't.
So as u can see most of the time, than the out side temp the cabin temp is the optimum operating temperature. this is why the vents of the battery are inside the car than out. It doesn't mean that u can't open shutters and travel but in average if u see most use A/C's when hot.
So i guess it's safe to say if your comfy so are the batteries.