Senators can be re-elected indefinitely, as there is no limit for the number of terms that a senator can serve in the United States government. Senators are up for re-election every six years.
At the end of each six-year term, every senator is required to run for re-election unless he has been specially appointed to his chair or has run in a secondary election to serve the remainder of a term. There are 100 U.S. Senators, two from every state. To run for a senate seat, the applicant must live in the state he wishes to be elected for, be at least 30 years old and be a U. S. citizen for at least the previous nine years.