Great question. I'm at a clinical psych PhD program and I can't speak for others but I work ridiculous hours. We have to teach and/or TA 2 sections for funding unless we have external funding (like grants or fellowships) or our research mentors pay us. Then we take classes, do research , and have practica (ours are really flexible though, number of hours vary, and we're sometimes doing more than one at once). I end up working 6-7 days a week most weeks, and it's not uncommon to spend well over 8 hours a day and pull a lot of late nights (but less on weekends because I have kids).
Let me add that I've been super grateful for my training but the expectations are high and the workload is super problematic...