So, my sister has this rescue greyhound called Mitzi. For some reason Mitzi has developed a habit of wanting to go outside every night at, like 3:30am to go potty. My sister says she was kennel trained as a pup and let out every 4 hours, so now she just thinks she needs to go during the night every night. If she isn't let out, she barks until someone gives in and lets her out. We know she can hold out the entire night because she has done it on occasion. Once my sister gets up for her, she doesn't get back to sleep. She's a kindergarten teacher and she needs her sleep! She tells me she is prepared to do anything except crate her. Mitzi spent enough of her life already in a box, and is quite good about doing what she's asked.
So, what's a good way to break such a habit?