Ball pythons are bred year around in captivity, but I think the reason most people use the fall-winter as their time to introduce and breed balls i because of the natural light and temperature changes, as well as the low pressure and precipitation that goes along with these months. It seems to just make sense that if you are going to pick a certain time of year to do all your breeding, that it would be during these months. It takes less work to change the light cycles and temperatures when that is what's going on naturally. Plus, we can't do anything to change the barometric pressure in our snake rooms, so letting nature happen and doing what we can to help exagerate what's going on naturally is the easiest and most logical way to go.