I took the bus once from Oslo to Sandefjord and I can confirm that it is a serious 'ball-ache' of a journey and seems to go on forever, last time I took it was in the evening so it was dark, I had fallen asleep and when I woke up and I had to ask another passenger was this the bus going to Sandefjord as we still had nearly n hour to go, never will I use that airport again to get to and from Oslo.