I took 5 APs as a sophomore (Euro, Phys 1, Comp Sci A, Calc AB, Art Hist), and I was fine. I had extracurriculars after school every day, so I got home at 6 pm 3 days of the week and 8pm 2 days of the week. However, the teachers at my school were excellent and never overloaded us with a lot of work. So, I agree with melvin above that it is highly dependent on the teachers at your school.