(b) Once the revenue bonds issued as provided in this article are no longer outstanding or the county commission determines that sufficient reserves have been or will be accumulated as of a specified date to pay all future debt service on the outstanding bonds, the service fee to payable services on a subsequent issue of revenue bonds imposed pursuant to section twelve of this article may not be imposed or collected for subsequent weeks after that date. Termination of the service fee as provided in this section shall not bar or otherwise prevent the county commission from collecting service fees that accrued before the termination date.