The enforcement by the state, county, city, or town of its lien for taxes on any lot upon which has been levied an assessment for any improvement shall not operate to discharge or in any manner affect the lien of the authority for the assessment, but any purchaser at any tax sale by the state, county, city, or town of any lots or parcels of land upon which an assessment has been levied shall take them subject to such assessment.
All liens for improvements shall continue until they are paid or extinguished or until the expiration of 20 years from the date of default in payment of the assessment or from the date when there was a due recognition of the indebtedness after default, after which time the enforcement of the lien shall be barred and the indebtedness conclusively presumed to have been paid.