We buy park hoppers good for the day we arrive until the day we leave DW. Usually, though, on the day of our departure we only spend a few hours at one park for last minute rides/attractions we didn't see yet (usually MK, although last trip we did MGM and MK), and then do major shopping at DTD. What works well is to not buy any souvenirs, or very little, during your trip and then on the last day, go to DTD and hit up all of the stores (especially World of Disney!) because they are sure to have anything and everything you want there. Plus, this way you don't have to worry about carrying bags around the parks. You could spend a lot of time at DTD! Your resort (assuming you are staying on Disney property) will hold your luggage for you until you are ready to pick it up - I love this privilege and definitely take advantage of it on every trip!