Any revenues of any and all projects in excess of the amount required to pay interest upon all bonds issued hereunder, to create a sinking fund to pay the principal of such bonds, when due, to provide for the operation, maintenance, insurance, taxes, and depreciation of such project, shall not revert to the general fund of the municipality. However, at such time as there shall be outstanding no revenue bonds issued by the municipality, any excess of revenues may be transferred to the general fund of the municipality in such amounts and at such times as the governing body of the municipality may deem proper and feasible.