The really interesting thing is that a few years ago, I had the opposite situation occur to me. Not sure why. We were staying at Animal Kingdom villas before Kidani village was open. I rented one room for my family, and another for my brother's for a particular span of time. Then, later, I extended my family's stay for another 2 days (my brother's family was arriving Monday, and we arrived Saturday). We had two separate reservation numbers for our stay. I was concerned that they were going to have us change room, but, no, we stayed in the same room. The only minor irritation is that they never sent us a receipt for the first part of our reservation--we had to go down to the desk to get it. I like to review the bill for charges to the room, so, it was important to me. They must have changed the policy in the interim, because I just changed a reservation from June to March (end of school year vs spring break), and it was for a different number of days, and we kept the same reservation number. I have changed resorts, also, and kept the same reservation number (suits me fine, because we don't do the dining plan every time).