I actually did get them to do this for me on an award stay. Had booked 4 single nights in a row at one hotel (always easiest if I am unsure of my flights) and the fifth night at the airport, then I saw I could get the 5th night free, if I stayed all at one hotel. I called and had then merge all reservation into one and paid for 4 nights and stayed 5. (FYI it was in Scottsdale during Giants spring training, so hotel was all full up).