Regardless of whether you previously registered or voted from overseas, you should send a new Voter Registration/Absentee Ballot Request form to your local election official every calendar year during which you would like to vote, as well as whenever you change your address. Send this in as early as possible to ensure that you are registered in time for election day!
You may also need to re-submit the form if you indicated that you only wanted a ballot for one election, versus all ballots in that calendar year.
Never assume that your ballot will simply be sent to you without sending in a new Voter Registration/Absentee Ballot Request form or having direct confirmation from your election official that you are on the voting rolls. Always confirm that you are on the list to receive an absentee overseas/military ballot for the upcoming election.