We haven't cruised on RCI but from the sounds of posts here it appears their service on B-2-Bs is the same as on those lines we frequent. We have been on quite a few B-2-Bs but only one time have we had to change cabins. As already outlined, the cabin crew did most of the moving for us while we were on a shore excursion.
Today it is even more refined, one doesn't see much difference between a B-2-B and a continuous cruise except that so many new guests suddenly show up and your nearby stateroom mates have changed. The lines are pretty coy anymore and don't usually label cruises as back-to-backs, for instance, most of these so called "World Cruises", "Grand Voyages", etc. are simply multiple segments (or B-2-Bs) packaged together and labeled with a single fancy romantic name. One time we booked an almost three month cruise titled "African Explorer" which was actually two six week segments but we didn’t know that. On a number of these we didn't even realize there were various segments until we were on board and other guests would mention they are getting off here or there.
One thing to watch out for is that when you board make certain your guest card is for the entire voyage, if you have to get a new one for the next segment don't get off the ship until you have. A few weeks ago we were on one where they handed out those "in transit cards" but we didn't need one since our original guest cards had the correct dates on them. The ship's company usually looks at your guest card twice when getting back on board, once at the gangway and then when they scan your card in order to indicate you are back on board. All the initial crew person at the gangway is looking for on your card when you get back on is to see that it has the correct voyage date.
One time a fellow was telling me about the time they got off and couldn't get back on because their cards were for the "last" voyage. After he mentioned that I looked at my card only to discover that it too expired that day and I was just about ready to get off.