Before I began my full-time job with studying for the MCAT last summer, I was working out 4 days a week for 2-3 hours at a time. I didn't do any exercise for a solid six months, but now I am slowly climbing back in to it, generally dedicating at least 30 minutes every day to cardio and pushups before bed.
My problem was I was way too in to lifting. I had previously lost 100 pounds and was positive I needed to get swoll, so I lifted until I benched 300+ pounds. Realistically, it's not something I could maintain while studying as much as I was/will. I know plenty of people in medical school who workout 3-5 days a week; however, they do not dedicate 2-3 hours a day to it. Rather, it's more of a 30 minutes cardio/30 minutes lifting routine. It's definitely doable.
I also know of a fellow meathead in medical school who was similar to me in the "taking weight lifting way too seriously." He got through 1st year fine, but then didn't do so hot in 2nd year because of his dedication to the weight room. He ended up having to retake his 2nd year. Moral of the story: know what's more important. It's easy to get addicted to exercise.
Also, importance of life events outside of medical school will play a large role. Personally, I am an introvert, so I need some rejuvenation time all alone. Sometimes I have to skip a workout to get this, and that's just fine. You just have to find what's most important!