I've not bred snakes....I've only read a ton about it and seen some of the biggest breeder's incubators first hand. I don't believe you're supposed to turn the eggs at all. In fact, breeders are very careful to make sure the "top" of the egg remains oriented toward the "top" as best they can when removing the eggs from the snake and putting them in an incubator. So long as the incubation medium and environment is correct, you shouldn't need to mess with the eggs at all.