I don't remember the last time we had our central heating on at my family's house. I'm not sure if it even works. I think it technically does, but typically heats the second floor about 20 degree warmer than the lower floor and has an odd smell when first turned on so we don't really use it. We have space heaters in some parts of the house in the winter, but for the most part just try to dress more warmly. I guess we probably have the heat on when it is around or below freezing outside (40 degrees Fahrenheit maybe, but probably not 45), but it doesn't get that way in the Atlanta area all that often for for very long. (Sure, it will go below freezing at night in the winter, but usually get back up to the mid 60s by early afternoon.)
We used to like to have the air conditioning on to keep it below 71 all year round, but in the past few years (likely because my mom is through menopause and so doesn't get so many hot flashes now) we probably let it get up to about 76.
In my apartment I typically don't like to turn on either the heat or the air conditioner, and only do so to compensate for when my roommate has been using the other one too much. That means I'm more likely to use the heat in the summer and air conditioner in the winter, but neither for very long. In general there is no need to use either in our apartment as the building is heated/cooled enough.