Another useful bit of knowledge is that Norwegian hotel prices in the bigger cities drop markedly on Friday & Saturday nights as the Businessmen leave town.
I've been juggling dates for Oslo for 4 years to ensure I can afford the Opera Hotel which I regard as the best in Norway for the train traveller.
Perfect location, efficient friendly staff, a superb breakfast and every amenity you could desire.
But it's pretty dear Sunday through Thursday nights.
Dave