You may also try calling the insurance claims dept to see if there is anything you can do to assist speeding up the process. Sometimes it just takes a couple of calls (and sometimes back and forth from provider to insurer) to get this moving along. Be patient, but persistent in the urgency to have this reviewed/approved quickly and you can hopefully have some positive results quickly.
As to your original question, when I was able to take Remicade, I took it once every 6 months.