In the first conversation I had with a student at the school I visited last Friday rendered a great bit of advice. I asked him to describe the workload from his first year, and subsequent years. He told me he had set ground rules for himself early on, with his wife's encouragement, that he would only work Monday - Friday until about five or six. It meant he came in early each day, but it also kept him from taking his work home. He felt that if he started taking it home in his doctoral program, he would continue doing that once he became a professor. He considered his doctoral studies the beginning of his career, rather than a transition between his past life and the career of academics. I could definitely see his point.
I hope I can manage to set those ground rules for myself - my wife and I had already discussed similar ideas of separating work and family - but I cannot say how easy that will be until I delve into the first year. Still, like with any other career, a job can take every minute a person will give it, until there is no time left for life beyond. A career in research is certainly no different. The beauty is I can define for myself how I spend my time, and when I am going to stop for a given day or a given project. Certainly I will have to meet the demands set by others, but I will largely be able to set my own schedule and path in this new life.
P.S.: I will be recording my thoughts from the discussions I had with the people I visited with that Friday. Each had something important to share, even if they didn't intentionally do it. It may grow boring for anyone still reading, but I wanted a record of these thoughts for myself.