Our fist cruise was 7 days and have not taken a shorter one since. We went on a 14 day Hawaii cruise and a 17 day Med/trans Atlantic cruise. Everything after that has been at least 12 days.
I don't think that I can go back to a 7 day cruise.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08