I think you are very concerned with "cookbook" procedures for cooling snakes.
To ease your mind and give the snakes a choice, you can meet 1/2 way. That is, allow the ambient temp in the cage to get down into the low 60s (high 50s OK too) and still provide some heat on one end if you can, at least during the day. This setup allows the snake to choose and allows it to ease into a cool mode.
I've bred kings with the above setup. It seems to me that they choose what they need to produce. To produce viable sperm, males likley need some kind of queue. That may be light cycle (reduced light) and temperature change. But it doesn't have to be 55 deg for 2 months exactly. Otherwise kingsnakes in South Florida couldn't breed. Whose cooling them? They still produce, and they aren't all that much different from kings that live in areas that get colder in Winter.
-----
Mark