Thank you both very much for the very informative replies. We are going on just a nineteen day cruise so a bottle of rum might last two or three hours. If however I want to enjoy this cruise and not be carried off in an alcoholic stupor, then just the one bottle will be more than adequate.
I remember once when dining at the captain's table, I asked for a glass of Guinness, the other guests looked at me in total disbelief. Their eyes all looked like mini ping pong balls, the captain however looked at me with a big grin and said.... ,Finally, finally I can enjoy my favourite beer' 😊
The rest of the evening was a huge success, our table was the last to leave having taken a hint from the waiters who were all resetting the tables for breakfast but I confess this was pre covid .