Always a chance something can go wrong. Here is our experience. Early in the cruise we went to the Pursars desk and requested an early "walkoff" number. They disembark walkoff's in groups of 50. We were in the second group. Our flight was 10:20am. There was not a long security line at that hour. We were sitting at the boarding gate at 8:30. As previous posters have said "if you are not comfortable with the time by all means attempt to change it". Would we hang on to the 9:30 flight ? I think we would.