Administrative Rule 338.7102 (1) states that the renewal of a prescription is required at least once every 90 calendar days, unless the termination date is otherwise stated by the prescriber on the prescription.
If the prescription does NOT list an end date, it expires in 90 days.
If the prescription states a time period such as TIW x 6, it expires in 6 weeks.
If the prescription lists an expiration date, it is valid through that date.