What's up with the Jury?

I don't mind doing my part and serving on the jury just like everybody else in the United States but, come on already. I was summoned for jury duty 4 times in a year and a half and then I have not had a summons in like 10 years so I figured it was due pretty soon. But, Thursday I get a jury summons in the mail and then Saturday I get a second jury notice to a different courthouse on a different date. What's up with that? Two summons from two different counties for two different courthouses, two different rosters two days apart... Pretty crazy! How do they select jurors now? Are we selected for Jury based on our voters registration? Because I haven't lived in one of these counties in over 3 years but, I just changed my address for my voters registration after the primaries?