It's one thing to take a one-week or even two-week cruise. It's another to set out to sea for six months, stopping on several continents and visiting dozens of countries.

World cruises are for those who want to see it all (or most of it all) in one shot. Multi-day stays in major ports allow you to go deeper into each destination -- including inland sights.

Though you’ll need a large chunk of time -- and money -- to go, if you can manage both, you’ll hit bucket-list attractions, from Costa Rica to the Great Wall of China, all with the comfort of a stable home base. Plus, you’ll claim status in the cruising world as an "all-rounder" or "worldlie."

Most world cruises embark in January. For 2017, ships in the fleets of Princess Cruises, Cunard, Holland America Line, Oceania, Silversea, and Regent Seven Seas Cruises (for the first time in six years) are all setting out on itineraries of 100 days or more. Oceania Cruises has the longest itinerary -- a 180-day sailing on the Insignia, sailing from Miami (there's a waitlist).

Of the remaining staterooms available for next year, fares start at $19,999 for an ocean-view stateroom on Holland America Line's 111-day cruise, round-trip from Fort Lauderdale to Central America, Asia, the Middle East, and Europe. Or, you can splurge on a concierge suite for a 128-day cruise on Regent Seven Seas' Seven Seas Navigator from $69,999.

If taking several months off isn't in the cards for 2017, block out time for 2018, when Viking Ocean Cruises will join the ranks of lines doing world cruises. Both Crystal Cruises ships will also embark on world itineraries in 2018, and Oceania will be back with another 180-day romp.