February last year on a big family trip, my wife and I booked two future sailings, when we got home we booked b2b in may.
On that trip, we booked 2 more future sailings on each cruise (for a total of 4), and split them up to have 4 new sailings.
Like I said, the easiest way to do this is
just book place holders and then rebook them for whatever. We listed Costco as our
travel agent and had no problems.
The only ABSOLUTE, is one person from the original booking HAS to always be on the reservation.
The huge advantage to just booking placeholders, is the deposit is the cheapest ($250) and it takes the least amount of time, you just fill out the sheet and they future cruise desk does the work and emails you the confirmation. You can also specify what travel agent you want to use. Then when you get home you can, in a more relaxed environment, pick your next destination.
On the other hand, the prevailing rate may go up in the time you get off the trip, or the ship could be fully booked.
As to what you quoted, from what I have understood in speaking to them, isn't that each cabin can book up to 2 rooms for a future cruise.... it is that each adult in the room can book 1 room on a future cruise - with a limit of 2 cabins. The way you do this is Adult one in room 1, Adult 2 in room 2. All future booking MUST be booked with a person currently on the ship. There is some gray area later on about taking them out of the room and switching things around. Officially the OBO room is still valid so long as one person on the original reservation is still in the room at sailing.
There for, if you want more then two cabins on a sailing, cabins 3 and beyond are booked at the standard rate. This prevents a couple from going on a 3 night cruise and then, while on board, using the OBO to book a dozen+ rooms for a huge family trip.
Outside of that, the onboard discount is advertised as being transferable to any non-blackout cruise in the 24 month period after the sailing. What you chose to do with them after you get off the ship seems to be less regulated then what they let you book while on the ship.
Other people may have different results, but that has been my experience.