Affidavit of mortgage renewal; time limitation, effect

Every mortgage not renewed by the affidavit of the owner or 1 of the owners thereof, or by the affidavit of the agent or attorney of the owner or owners, showing the amount remaining unpaid on said mortgage, or by extension agreement, filed in the office of the register of deeds of the county in which the lands are situated which are covered by said mortgage, within 30 years after the due date as set forth in said mortgage, or when no due date is set forth in said mortgage, then within 30 years after the recording of said mortgage, shall be considered as discharged.