I'm a second year Bachelor of Science student at UQ, majoring in Mathematics (Analysis). This semester I did two maths courses, one physics course and a religion course and ended up at uni for 15 hrs one week, then 18 the following week (due to pracs being scheduled once a fortnight). I work as a supervisor on weekends and Thursday nights and dropped back from three shifts a week to two this semester so I could have a day on the weekend to play catch-up and get on top of all my work. I bludge far too much and should currently be studying for exams. Starting next semester, I'll only be doing three subjects. When I'm at uni, I tend to get sick very easily so doing one less course a semester will hopefully let me rest enough to prevent any severe illness.
It's definitely manageable and nowhere near as strenuous as HSC, where you'd be at school for seven hours a day and then be expected to study for several hours when you got home at night.