The assessment shall be a lien upon the property affected thereby, with priority as fixed in Section 5373, until the bond issued to represent the assessment and which it is hereby declared does represent the assessement, and the accrued interest thereon and the penalties, if any, shall be fully paid according to the terms thereof, but which lien shall in no event continue beyond four years after the date of the last principal coupon attached thereto, and for the purposes of Section 330 of the Code of Civil Procedure and Section 2911 of the Civil Code said date shall be deemed the “due date” of the last principal coupon attached to said bonds.