Echoing a couple of other comments. My oldest did 11 AP classes and she's one who thrives on being busy. She also rowed crew. The amount of down time in college is leaving room for anxiety and she needs more to do. The energy needs to go somewhere.

She is also the fastest reader I have ever seen and remembers what she reads. The advantage in this can't be overstated.

My second child took 8 and that was a lot for him.

Speed readers have a huge advantage. I have one, and he gets 3x as much done in half the time as my typical kid.