Yes, we've done it, and plan to continue to do it!
Our last trip was only going to be 4 nights, Su-Wed. Then, we got a much better deal on airfare to depart on Saturday. Since we weren't going to get to the resort until about 8pm anyways, I had initially thought about getting a room at Pop Century for the night and then switching to AKV in the morning. Silly me....I forgot that I had 19 points leftover (that I was going to bank). Turns out, Saturday night in a value studio at AKV was 19 points. So, now we could add a night without adding any more money! Amazingly, there was one available at 6 months.
The room was small, but we never unpacked. In fact, I had bell services hold our Magical Express luggage until the next day when we checked into our 1BR. When we drive, we usually arrive in the mid-afternoon. When we fly, we usually arrive in the evening, so it is silly to "waste" the points on a 1BR when we will only be using the room to sleep.
The other advantage of splitting up our stay like this is that we can add a
DDP to only part of our trip. We enjoy TS meals, but we do not like to plan an entire vacation around ADR's. So, for that trip, we added the DxDDP to our 1-night studio reservation. We ate at Boma for dinner and then Boma for breakfast and LeCellier for dinner the next day. We had our mugs and snacks to use throughout the rest of the trip. In April, we are taking my parents and doing something similar. The first 2 nights, we will be in 2 studios at Jambo. Then, we will move to Kidani for three nights in a 2BR. We've added the DDP to our 2-night stay so that mom and dad can enjoy Boma and LeCellier without the "sticker shock"

of holiday pricing.
The only downside, especially with little ones, is that you could potentially be "homeless" on your switch day. You have to be out of one room by 11am and you may not get your next room until after 4pm. If you plan on being in a park all day, then it is not a big deal. Just make sure your "switch" day isn't a day that you plan on hanging around the resort. You could get lucky and your second room could be available before 11am....then you'd have 2 rooms!