Here in L.A. County, we have to call in every night for a week. If our group is "called", we have to go in the next day - then it's one trial or one day. Last time I had to go in, it wasn't until Friday and court was slow, not many new cases. We got to be excused at lunch time.
Also, in L.A. County the only people automatically excused are police officers. There was actually a judge empaneled on one jury I was picked for - but the attorneys excused him right away! lol And that was the only jury I actually was empaneled on - but I was excused when I realized I was allergic to the new carpet in the courtroom!