Personally, I wouldn't do it. I like to unpack once and settle in and then that's my home for the duration. I don't even like when I have to make two reservations at the same resort due to restrictions on discounts (sometimes a 14 night max) because I might have to change rooms - although so far I haven't had to make a switch. I also usually have perishables that would need to be taken care of, so just loading up the car and leaving everything in it until I check in the next resort would not work. Plus, unlike the pp, it takes me longer than 20 minutes to pack up and more than 10 minutes to unpack.
However, if your trip is long enough that you would have time to actually enjoy both resorts, and you don't mind the packing and unpacking, then it can be a good way to experience two totally different resorts. For example, you could stay at a MK area resort and enjoy the easy access to MK, then move to an Epcot resort and enjoy the easy access to Epcot and DHS. Or you could stay at POP and hit the theme parks hard, then switch to FW for a few days unwinding and enjoying the resort activities. Since you are splitting POR and Poly, each resort has it's own location advantages - MK and Epcot are simple from Poly, and AK and DHS would be by bus from either resort so save those for POR.
I once read a post where someone was switching resorts every couple of days, and either going to three or four resorts during their trip. I can't imagine what that must have been like!