Trailers, excluding boat and construction trailers and trailers used in delivery, loading and unloading operations, to be used for storage or sale of goods or merchandise or in which commercial services are rendered for a period not exceeding two months. Prior to the expiration of the two-month duration of the conditional use the applicant may apply for one extension not to exceed 30 days and shall be permitted to continue the use until the decision of the Planning Board if all fees required for the application have been paid.