Thanks for the replies. It hadn't even occurred to me that people would cancel the insurance just before cruising... I guess I'm too honest, and I didn't get the insurance in case of changing my mind
I'm more concerned about the medical coverage, with trip interruption and lost luggage secondary.
I've been reading the details of Carnival's coverage, and while not as good as others, I guess it'll do for this trip. One more thing to know for the future!