Just returned from 63 night Serenade (first quarter World Cruise). We had one 28 inch suit case each, and one duffle bag each with "slide handles" that go over the top of those suitcases. Each of us had one rolling carry on bag.
In one duffle bag was a highly compressed 1.5 inch mattress pad, that I cut to size when we got there. (Yes those king size beds are not king size). Totally happy to have that as the mattress (though new) supplied by the ship was like a rock. One duffle had just about all of our medicine cabinet tossed in, plus favorite toiletries.
We are about to complete the last quarter (62 nights) in July. Will be repeat of the above. 😉