We've been on 4 cruises and I still overpack, although not as badly the last time. Last cruise I only brought home a couple of items that were not worn. I am getting better but I do think cruising experience helps out more than anything for packing. One time, in trying not to overpack, I forgot to take any t-shirts and ended up having to buy some. I do pack less every time. I never take more than 3-4 pairs of shoes. I personally don't care if someone notices that I am wearing the same clothes twice. I will never see these people again and I just don't care what other people think. I am on vacation to enjoy myself, not to worry about others.
We take 2 suitcases each because we take snorkeling gear, with beach shoes. We like to snorkel and don't particularly care to use stuff that other people have had in their mouths (I know, they are supposed to sanitize that stuff but I don't care). That allows us plenty of room in the luggage for souvenirs.