We have done one 14 day cruise and couple 11 day ones, the round the world cruises have a crazy number of stops, which would help, but most people cannot be gone that long. It's a very niche market looking at people that have money, they are expensive as hell and love the cruise lifestyle.My parents love them though the cruise across the North Atlantic was a bit rough. I read their marketing fliers and I want to know who signs up for their 3-6 months cruises that travel the world. I can’t imagine going longer than two weeks.
We did Alaskas out of SF three years ago, and boy sailing up that far gets really old, I can't imagine crossing the Pacific or Atlantic.