About 7-8 months, but they grow til about 14 months. And there are snakes large enough to eat humans. Especially the cartoon ones. Anacondas, Reticulated Pythons, and Burmese Pythons have been known to. I read a very LONG lengthy article on why, and it was inconclusive.
Cats can purr while exhaling and inhaling.
It can be very difficult for them. It's worth it to get health checks on Mom as she gets near term. It's certainly important to wait til she's a couple years old to let her breed. Go to the website. It's an attempt to get rid of excess energy.