9 CFR §590.161

When inspection service is not performed at any plant for a period of at least 90 days, plant approval shall terminate upon notice by the Administrator without further proceedings; provided, however, that this section shall not apply to any plant where the Administrator determines that such a plant operates on a seasonal basis and the inspection service has not been used as a result of such seasonal operation, or where operations have ceased due to extraordinary circumstances determined by the Administrator as not warranting termination of plant approval.