We are three retirees ( we need to travel on budget, but will do what it takes). Who want to visit Norway and Sweden in 2014 or 2015. We are are thinking to fly (from USA) into Bergen and take train tour to Oslo. Then fly(?) to Tromso to see NL. From there we could return to either Bergen or Oslo or go directly to Sweden. We have really good flexibility with time. I am guessing allowing two nites in Tromso for best chance to see NL. I read season for NL is Sept to March. We can come pretty much any time in that period. When is "best"? We'll be using planes, trains and buses...any advice here helps.