I used to live 35 miles out of town and in addition to work, I had to run errands in town before going home. I felt bad for my dog (an adult boxer). In the summer he had a dog door and made a right nuisance of himself (but he's so lovable, no one minded). I moved in with my DBF and his lovely shepard dog, and ... my old guy has a new lease on life! I realize you are talking about a puppy and not a lonely adult dog, but I am completely and forever more sold on the idea of a two (not three) dog house. One of my dearest friends once gave me a good piece of advice: only have as many dogs as hands - so you can pet them all at once.