We just returned and did 2 moves over 12 nights. We started our trip off-site at Vistana Villages for 7 nights. Then we moved to PO-R for 4 nights. When planning our trip, we decided to add one more night, but PO-R was booked for the discount code we had, so we added 1 night at the Poly.
As far as switching goes, I really think it depends on how much stuff you have, and how organized you are. It also takes a little planning. We had a car, so we moved ourselves instead of relying on the resorts to do it. Our first switch was planned on a non-park day, so we didn't lose any time in the parks to do it. Our 2nd switch was on a park day, but wasn't a problem. We packed most of our stuff the night before, loaded up the car in the a.m. and headed MGM. Mid-afternoon we checked-in at the Poly, went for a swim and headed to MK for enight.
We enjoyed getting to stay at several resorts, but did wish we'd had more time at the Poly. I think that splitting a 6-night stay would be alright, but don't know if I would do it with less than 6 nights.