Pack light has always been a favorite saying of mine. When a person could check a 70 lb bag, one could slip in a few books coming and going and not have to worry about going over the limit. Now that the airlines have reduced the weight to 50 lbs per bag for the most part, it can be very frustrating packing for an extended trip. It really increased the travel stress level when the weight limit was lowered. Why worry about the overage on one bag, when you are allowed to take 2 bags at 50 lbs each in addition to a carry on bag. Using a very accurate scale system, I have compared the distribution of packing two bags compared to one. If one bag ends up weighing 53 lbs on departure, I know it will weigh 60 lbs or more on the return. By using 2 bags, one can redistribute the weight (35 lbs and 43 lbs for example) and still have available weight amount to bring home the usual book purchases. (I travel with someone who loves books.) I know we will be bringing home an additional book weight of approximately 30 lbs or more than the departure weight. Four suitcases departing underweight will return at 50 lbs or slightly less.
These two suitcases should be of different sizes so that they can be placed inside each other once aboard the cruise ship. Some vessels have a special storage area for suitcases. Others do not. If you can take a large suitcase, place the medium size suitcase inside the large one, and place the carry on bag inside the medium size bag, and the nested suitcases will easily fit into even the smallest cabin. Now that the bags are nested, they provide the perfect solution for persons with back and circulation problems who are used to sleeping with the legs elevated at night. Some cruise ships have wedges available from housekeeping to place under the end of the mattress at the foot of the bed to create an elevation of the legs. Other cruise lines do not. Easy solution. Take the nested bags and place them under the foot of the mattress, and it creates the necessary wedge. The bags are then completely out of the way.
Bottom line: It is much cheaper to pay a porter to handle 6 bags (2 people) than it is to pay for one overweight bag. Secondly, you have a nice non-collapsible traveling sleeping "wedge".