Look at it this way. Your passport is good for ten years; you may take more cruises or travel international. When you factor in the price to get your passport, and it is good for ten years; it's pretty cheap.
Freedom of the Seas Dec 11
Allure of the Seas: Jan 11
Voyager of the Seas: May 09
Splendour of the Seas: May 07
Explorer of the Seas: Jan 04
Majesty of the Seas Jan 99
So how do you all carry your passports? I've never had one before. Sure wouldn't want to lose it.
Carefully! I have had a passport for 53 years and have never lost one.
Carnival Liberty New Year's Eve 2007
Liberty of the Seas 5/2008+11/2009
Allure 1/16/ 2011