In my experience, a female will spend the majority of her time on the cool side while building. Is it 70, 80, or 90%? I don't know. But when I pull the tub out I tend to find her on the cool side or bowl wrapping more times then not. As far as eating, girls can go off feed regardless of follicle development and some females will continue to eat through the whole process. Every snake is different. Really the only way you'll know is by going through a breeding season with a female and seeing her particular trends, to gauge against the next season. If she has stopped eating but is still putting on size and weight, that is a pretty good indication she is building. The other thing to look for is the "Glow". When a girl is building towards an ovulation, they typically brighten up dramatically, especially around the head. A normal female will almost look like a fire when she glows. If you are seeing a dramatic color change (brightening) in your girl, that could also be an indication of building.