I've never done a three resort split stay (though I sometimes dream of 3 days at AKL, 4 at Poly, 4 at BC/YC). I have done two resort splits, and I find it super easy. Our first resort is usually a 2 night stay, so I just pack a small suitcase of clothes for that resort. Dirty clothes go into a bag and into that suitcase at the end of our two nights. Toiletries are packed in a smaller backpack and are really the only thing we need to pack up at the end of our stay.
We also schedule a park day/resort night on the day we move. We just take our bags to bell services in the morning and head out to the parks (I have packed my laptop in a locked suitcase without a problem...smaller electronics go into our daypack). We head to our new resort anywhere between 3:30 and 5 to check in (I haven't yet received a room ready text for the second resort, but our room has almost always been ready when we go to the desk after 3:30). Once we're in our room, a call to bell services has our bags up quickly. After unpacking and a quick nap, we hang out at our new resort for the evening, playing in the pool, going to dinner, etc.