Ames, when I lived in Baltimore City, their policy for jury duty was “one day or one trial.” That means that you go sit in the court room. If you are not picked for a jury, your service is completed at the end of the day (until the city summons you again, usually about 2 years). If you are picked for a jury, your service is completed at the end of the trial, and you can’t be called again for 3 years.
I was picked twice. The first time I was an alternate juror on a murder trial – one guy shot another in the eye and killed him over $10. The other trial was a civil lawsuit which lasted two weeks. I, by virtue of being picked first for the jury, was the foreman for the jury.
I would advise against skipping jury duty. The very first time I went I saw a judge signing bench warrants for those who did not show up for jury duty that day. Besides, as long as you’re sitting and waiting, you can pull out a sefer and learn the time away. (Our jury room also had movies, one before lunch and one in the afternoon!)