You can try to keep your bounce rate low. You can interlink your hubs with similar topics and target only a specific audience. This will allow you to predict when you will be getting alot of traffic and when it will be low.
The rank is not very significant, just make sure it is over 50. It will change depending on many factors, most of which we don't know. What I do know is when I get alot of traffic it goes up, the opposite happens when no one is really reading the hub.