With a bit of research, it's not difficult to book all of the tickets yourself and select the times that work best. It saves quite a bit of money but also allows you to do seat selection on some of the trains. I've got all my tickets booked for about 3 weeks from now so we'll see how it goes. In my case I'm doing Bergen, Voss, Gudvangen, Myrdal, Bergen. The times just seemed to work out better.