From my experience, the NextCruise promotions require new bookings. The good news is that you can reprice your existing reservations until final payment If better prices or promotions , including on board credits, are available.
I have done this only by manually stepping through the itineraries by date. I have contacted RCL directly, and they employ the same method. Time for a system upgrade.....
I believe it has to do with the payout odds on the bet. Generally, slot jackpots are frequently over 1000-1. I have seen the same W2-g action on progressive payout hits on tables that exceed those odds. It may be lower, as low as 600-1
We have been looking at that option also. OA on 3/15 is week 2 of a B2B ... and we have to switch rooms already! That might be the justification we need (not that I need a great deal of addition motivation) We find the room very interesting ... besides, it's only money! ??