Hi Neil, that's some info, I can "digest" also.
What I have done in the past, is a "little fishing."
What I do is call Carnival and tell them what deck I am interested in and see if they have a room available in the balcony, window, or inner, of what I want at that time. (Of course they do not know that I have already booked my cruise.)I will then ask if they are giving an over 55 discount. Before they just happened to be doing that when I called, as I contacted my TA about it, and that was "another story."
My TA told me at the time we booked that they were NOT giving any over 55 discounts at that time, which I'm sure was true. To make the long story short, she did come through, although it took a "nice" email from me to the owner of the company, explaining what had happen, and she did come through. More than likely she didn't like loosing some of her commission.