I don't know if you can ever take time off when you're running other people's money, unless you've got someone else working with/for you. Maybe not even then. Two books you should read if you haven't already:
Pit Bill by Marty Schwartz: the chapters about his investors pulling their money out of the fund while he was lying in the hospital critically ill. Also the brief chapter "Sorry Dad, You're Fired" which discussed vacations specifically.
Confessions of a Street Addict by Jim Cramer. I lost track of how many family vacations he ruined because of a crisis at the fund, and the marital tension it caused even though his wife was a trader and knew what the pressure was like, and even though he had a very competent partner and staff.
Monroe Trout also said that he felt he could rarely take time off.
Of course none of these guys were trading a fully mechanical system (even Trout), so they really did need to be at the helm at all times, or had reason to feel they did. You and I just might be able to take some time off provided we've made arrangements for the trading to continue in our absence.