Years 1-3 I worked around 30 hours per work. We usually had one day off (or nearly the whole day on Thursday) from classes.
My work hours usually were Mon, Tues, Wed, Fri 6-9pm, Thursday/Saturdays 8 hrs each, and Sunday 5 hours.
Total work week was 3+3+3+8+3+8 (sat) + 5 (sunday) = 33 hours per week.
4th year was different b/c of externships and I could only work M-F 3 hours each from 6-9pm, and kept the weekends the same.
Total work week was 3+3+3+3+3+8 (sat) + 5 (sunday) = 28 hours per week.
The great thing about Target Optical at that time I could study during those hours a lot since the Optometrist usually left at 5pm. Saturday was my only really busy day. It helped me focus and use my time wisely but all of this came at a price of not being able to go out at night or the weekends.
My biggest regret was living by myself during year 2, 3 and 4. If I could have learned to live with 1-2 room mates it would have cut my loan size down by a lot more.