I think it depends on where you are going and what you like to do. For instance, we did a 7 night Caribbean cruise and I couldn't imagine being on the ship any longer. Not that we didn't have a great time because we did but for me I can only take so much down time laying in the sun and relaxing. July of this past year we did a 11 night Mediterrean cruise and it was perfect. I didn't feel it was too long at all because we had just the right amount of relaxing and alot of sightseeing.