I sailed Norwegian Majesty three times; four if you count her previous incarnation as Royal Majesty. Three of the four trips were Boston-to-Bermuda. Despite the same ship and itinerary, each cruise was different. I'd find new places on the ship, meet new people, and visit different places in port. Still, it was exciting to board the ship... each time, it was like coming home.
There have been a couple of other ships we sailed more than once, and there are others I would sail again without hesitation.