To those contemplating living separately while married: I had this experience while in graduate school and it is the one that I regret the most. My husband and I were married for four years and lived apart for a good portion of that time, since my school was too far away for either of us to commute. We still saw each other every weekend, and occasionally in the middle of the week, which was okay for a while. However, there comes a certain time point when you are just no longer happy with the arrangement: it is heartbreaking to go separate ways each time the weekend ends, and phone calls are not enough. It feels like you are missing out on many things (some as simple as having breakfast together or taking walks at night) that are a part of being with the person you love every day. Granted, by the time I came to that realization and started to think about ways to finally live together, my husband already had an affair and we ended up getting separated. My lesson from this is that I will never, EVER, have a long-distance relationship, much less a marriage again. Also, my parents said that the long distance may not work because some married men need to come home to their family every day just to keep their heads straight (which may or may not be true, I don't know).
While I do not want to discourage anyone from considering a long-distance relationship in med school, my own experience with the long-distance marriage has been a painful one (irregardless of the affair, because I thought we were fine as a couple and quite happy), so I wanted to share that.