Hi!
I also work 10 hour days so this thread spoke to me. You just have to make exercise a priority. Find out whether you prefer working out in a gym or at home. I find the gym has a great selection of equipment but I hate all the people during the busy hours (when I have to go). There are a lot pf pros and cons.
I work out 6 days a week, which is not for everybody, but I've found success following the Body for Life program. I used to get up at 2:30 am to go to the gym (I have to be at work at 6am) but I couldn't do that for long. Now I wait for my husband to get off work and we go together at around 8pm, then I immediately go to bed after a shower. I sometimes have a lot of difficulty falling asleep but I don't know what else to do short of going really early.
I think Most people would be happy following a program of working out 3 or 4 days a week. Just start doing it and you'll be surprised how your schedule will fall around it!