We are Disney veterans as well as DVC members. We will frequently change rooms during a trip in order to experience all the different resorts. On most trips, we have been able to request a late checkout (usually no later than 1), but very rarely have been able to check in before 3/4 depending on the resorts specified times. (There is NEVER a late checkout with a DVC resort!)
One caveat......on EVERY trip, bell services has managed to miss-place our luggage if we have had it sent over. It either never gets sent, or is "lost" upon arrival at our new check-in. It usually has taken at least an hour to clear this up. The worst was not getting our things until 11 that night! (Including the kids PJ's & toothbrushes!)
Now, if we plan on switching resorts, we drive either our own car or a rental & simply store our luggage in the trunk!
J