Personally I would separate them ASAP. They will mature and go into breeding mode too early and without the proper body condition. I did that with some Arizona Mountain King snakes, I thought my female was going to die because she was so thin and wouldn't' eat because she went into breeding mode. If I were you I'd only put them together when they are fully mature and when they have a decent body weight. And with most snakes if they have eggs too young it can kill them, or so I've heard.
Those are some beautiful snakes by the way! Apparently the babies have a tough time feeding and will sometimes only take small fish! I've never heard anything about these being venomous, not even rear fanged.