I dont use gestation periods as i dont believe you can know when they are pregnant. I know there are averages but i just dont go on that. I provide gravid females with above normal temp gradients. They tend to sit in the hot spot all the time. They also spend lots of time hiding.
I use ceramic 100watt emmitters. I have never in my life burnt a snake on them. Reptiles only burn themself when they are cold! Their deep tissues dont warm up as fast as their epidermal layer and they dont realise they are burning till its too late. I do suggest light cages for people that have not used ceramics before.
My room fluctuated between 9-15 C degrees celsius at night. I can of course manipulate their night temperatures with my day/night thermostats.