Occasionally, I try letting them out anyway. If I let both of them go, it takes forever to get them back. When I take them out one at a time, they are a little better about staying closer (especially Starbuck), but then the other one goes a little wild in the house, or dog yard, with jealousy.
Today, Starbuck made a break for it when I let them into the dog yard. Thankfully, I was able to keep River contained while I tried to coax Starbuck back. When she finally made it back in, I decided to let River have some free time. This time, I brought a pocket full of dog treats. She still didn't come right when I called, but she didn't go as far and came back quicker than usual.
Later, I tried let each one out again. They still weren't the best at coming to me when I called; although they generally stayed within sight. Interestingly, they both responded quickly to the phrase "Let's go back in." When I said that, each of them headed to our door--even if River did come up to me expecting a treat first.
I still don't trust them both out together.