I'd say its pretty clear that they are friends who have moved way beyond the days of Future Echoes and Lister telling Rimmer up front that he doesn't actually like him. There is definite affection when Rimmer leaves to become Ace, Blue explores Lister missing Rimmer (although viewing him through rose tinted glasses). I think they are the sort of friends who would drift apart quite quickly if returned to a normal situation but in the environment they are in their shared experiences and adventures have formed a bond between them. The old Rimmer would have resented Lister being the hero at the end of F&S but the new Rimmer did a sort of awkward little dance and tried to fit in. beautiful to see. :P What is odd about them is their living situation. Why continue to share a room after all these years on an essentially empty craft? I sort of get the feeling that it's become a living room with the bunks kind of just preserved out of nostalgia and that Rimmer and Lister probably have their own rooms.