We have done longer cruises on Deck 4 on the R ships. Nautica three times and Insignia on a Sydney to Papeete in either 4043 or 4045 which are our favorite two cabins. The 4049 cabin we would suggest is preferable to the 4055 for a couple of reasons. If you check a layout of the R ships, you will see that 4055 is right near the public area of Destination Services, Reception Hall and Reception Desk...actually the first cabin in that hallway. It is also next to the area where the gangway is often set up for passengers to disembark when the ship docks. You are also right across from the door that crew uses to come and go from the reception desk.
Having said that, the good news is that you are extremely convenient to all of the above mentioned services, GDR one floor up with no real walk at all, and one floor up to the show lounge, boutiques and Martini's. We find them to be extremely convenient and have three more cruises booked in 4043 or 4045. We rarely need to use an elevator except rare instances when we go to Terrace, the pool, and, of course, not-so-rare occurences when we enjoy Toscana and Polo. We feel the starboard side (odd numbered cabins) on Deck 4 is preferable to port side (even numbered cabins) due to traffic to Medical on port side hallway.
Another side benefit of Deck 4 is that movement is much less of an issue. We have never had motion sickness anywhere, but came close leaving Sydney trying to outrun a wind storm.
Enjoy your cruise!