Sorry for bringing up an old thread...
For anyone searching for transit hotels (free) - if you book a promo fare (booking class O) then you do not qualify (even if your shortest connection is over 8 hours)... I upgraded to J using miles and still was not offered the hotel
You are offered the hotel for US$125 for the stay or the contact details on the airport hotel where you can rent the room by the hour (min 3)