I know many travellers do this already, but what my husband and I do when travelling is each pack 1/2 of our clothes/shoes/bathing suits (if you are not AN!) in each other's suitcase. At least then if one suitcase is delayed by a day or two, one person isn't completely without a full wardrobe!
On our last trip to CSS, we met a couple who travelled on a direct flight from Canada and the airline lost the guys suitcase. His wife was fully outfitted in her bathing suits/daytime wear/evening wear, but he was sadly walking around the resort in his travelling shorts for 3 days and was quite upset about the ordeal. He managed to borrow a button-up shirt from a fellow traveller for one evening's dinner, but he was an unusual size so he had a difficult time to find suitable clothes to purchase.