I have gotten into the habit of bringing Lucy and Gunner in together. They don't go out in the same paddock but they are very close to one another. They are always the last two out and if I bring in Lucy and leave Gunner out, he goes ballistic. It's easier to bring them both in at the same time as long as they behave themselves. I think it's also good to occasionally lead a horse on the "incorrect" side just in case you ever need to in an emergency, for instance if you fell on a trail ride and injured your right arm and had to use your left arm to lead your horse.