Looking for suggestions on the best place to spend the night along the NIN route. Planning on going end of May. When do I need to buy tickets by?
End of May should not be a peak season for train travel. We did the Nutshell during the start of Easter Week and trains (and every mode of travel departing Oslo) was sold out and packed. May Day, Whit Monday and May 17 are holidays as is June 23.
That said, if your plans are firm, having tickets in hand are a comfort. If you plan on self-booking train travel through the NSB.NO earlier booking may save you some Kroner if take the Minipris advance purchase fares. The Minipris fares are booking dependent and savings drop the closer to travel and as discounted fares are purchased.
You should buy the tickets as soon as you know the date of travel. When you reserve your tickets you do so using a calendar on which you click the dates you want. If the date is "clickable" then you can buy tickets for that day. If the date isn't in bold, meaning it's "clickable", then tickets aren't available yet because it's too early. Right now tickets are on sale through early June so you need to get tickets for May as soon as possible. Not high season yet but the tickets will be significantly cheaper the earlier you book. We booked on the first day possible for the date we wanted last summer and it was quite inexpensive compared to what we would have paid even a few weeks later.
I would choose Geilo if you'd like to stay an evening in the mountains, or Flåm if you'd prefer to be on the fjord overnight. There's definitely more activity/things going on in Geilo than down in Flåm. The prices on the norwaynutshell.com site are not overly inflated. I suggest booking the nutshell one-way only. It is cheap and easy to fly back to Oslo.
I recently (March 6) self-booked our NIN for May 21, and I was still able to get the minpris for the train to Oslo.
My understanding is that peak season starts in June, but since we are doing it all in one day and are flying to Bergen specifically to do this, I didn't want to take any chances.
I had to telephone in order to book the Bergen to Voss leg (if you are going that route). It is a local train and not bookable online. When I called, the person I spoke to indicated that reservations are not really necessary, but I felt better making them anyway. The only part I was unable to book in advance was the bus from Voss to Gudvangen.