While I don't disagree with kcashner's sentiment, I don't think this is so cut-and-dried as is laid out here.
First of all, if you have to reschedule a cruise because of an illness, you will have to pay not only the change fee, but you'll also have to pay the current prevailing rate for the new cruise. Given that these illnesses are such last-minute, this usually makes for a significant price increase when you booked the cruise a year ago.
Second, I don't see anything in the insurance that says it will pay for the cost of changing your sailing date. It will pay if you have to cancel the trip, but that's only if a doctor is willing to state for the record that someone should not take the cruise (and this is a responsibility I have found doctors very reluctant to do in all but extream obvious cases).
Third, Anytime someone has reported that they saw a ship's doctor and were denied passage, they didn't get to just cancel the trip and file an insurance claim for a refund but instead were given some sort of a concilation vacation.
Again, I'm stating this all based on MY interpretation of the insurance text (excet the part about doctor's reluctance... that I've experienced). Does anyone have PRACTICAL experience with this type of situation?
The one time I tried to look into postponing a trip because of illness,
DCL couldn't offer any help other than to tell me the cost involved in changing the trip because it was a weekend and the insurance company is only open for questions during the work week.