If you receive a jury summons in subsequent years, you do not have to get a new doctor's statement. You do need to call the jury commissioner to determine if your name is still on the permanent disability list. If you are called for jury duty and you are selected to serve, you must serve until the trial is completed. You have then met the requirement for that year. If you are called and you are not chosen, that also completes your requirement for that year.
Trials are usually no more than one to three days in length.
If you are regularly employed, your employer must pay you for the first three days of jury service. If you are self-employed, in effect, you must compensate yourself for the first three days. You should call the jury commissioner to discuss the conflict.