Contracts usually run for 8 months. I believe most of your pay (or a good portion of it) is held until the end of the contract to minimize departures. Most personnel will work 12 hours/7days for 8 straight months. The people live in cramped quarters, 2 per cabin, and have very strict rules governing them. I rarely see Americans in the service ranks, only in staff level jobs.
Maybe it fits your style. But recognize that 12 hour days with no days off does not allow you to roam the streets and nightlife of the ports. Employees on the ships have told me their favorite entertainment is for one to go into town and rent a movie and then 6-8 of them will sit in a cabin and watch it while eating popcorn.