Exempt means you don't report hours. My first professional job after college was with one of the big consulting firms. I reported hours, and I got paid overtime after 40. I was expected to log at least 40 hours a week on something -- could be internal/self-training or client billable.

In all the other jobs I've had I did not report hours. I am hired to get a job done. If that sometimes takes me 30 hours a week and sometimes takes me 55 that is what I'm expected to do.