Many folks end up pulling anywhere from 35-60 hours/week or occasionally above at hectic times. First year is usually less intensive, then it progresses upward from there, generally, especially once practicum starts. Several factors will influence average hours worked in a week, such as number of courses (factor in class time plus homework), exams, due dates, research related deadlines, whether you end up teaching a course, etc.
I still had time for a social life, though. I also found that managing hectic and constantly changing schedules grew easier with time because I learned hiw to balance work-life better. Then first year is largely an adjustment period.
An average day might be practicum or assistantship 8-5, evening class, next day morning classes then assistantship in the afternoon (evening free), etc. I found that there were a few evenings I either had classes or worked late and then a few evenings free for homework, etc. Weekends I usually worked one of the days and had a free day, although there were some times I just didn’t work at all on the weekend, particularly during those lovely semester breaks.
Things are broken up day by day so as to switch between classes, practicum, and assistantships/research, sometimes doing two of the three in one day. It worked pretty well for me because I like using different skill sets and having different roles, some less demanding than others to balance out the roles that required more energy/intense focus.
Edit: Those with families in my program sometimes took and extra year or more to finish so as to have more family time during the program. It’s a trade-off, though, to pay more and finish later than your cohort. It is a difficult sacrifice if there are little ones in the picture. Graduate programs in general aren’t set up to support families very well, unfortunately, due to the time sacrifice and financial sacrifice.