2-3 hours a day Monday thru Thursday (more for exams: 4-5hours starting about 3 nights before big exams, an extra 45min-1hr the night before quizzes). Nothing on Fridays (date night with the wife). 6-7 hours on Saturday. Nothing on Sunday: time for myself, play guitar, hang out with the fam, drink some beers, watch some TV (football during the fall).
This has worked very well for me so far 👍