We are seriously considering doing this. Our family purchased two DVC properties this past year and we plan to go several times a year. We would like to leave a lot of things down at Disney so we don't have to pack them every time we go. It will make checking baggage easier and we might be able to just do carry on if we leave all the big stuff down in FL.
We don't care for the water so we are thinking about things like a water pitcher & filtered water bottles. Sunscreen, toiletries, dryer sheets, detergent, umbrellas, backpacks, first aid items, kitchen items....
We are going down in about a month for a short trip and we are going to pack some of the stuff in our checked bags and then leave them down there in our locker. We figured out the cost is totally worth it with the extra baggage fees. Sometimes the cheap flights are the ones with baggage fees so this way a carry on is all we would need.
Came here to see what people were thinking but it looks like the conversations are pretty old so I thought I would add my thoughts! 
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Kim