Be sure to check your State Statutes. In Indiana, the mortgage is good for 10 years from the time the last installment of the debt secured by such mortgage or vendor's lien becomes due, as shown by the record thereof.
If no maturity date is shown, the mortgage will expire twenty years from the date on which the mortgage or lien is executed.
We can file an affidavit to extend the lien within the 10 year or 20 year period, whichever applies. (As long we are not trying to extend it to cover a new debt.)
I agee with Anon, any modification done to a mortgage should be filed to get the changes in the mortgage on record and to extend your expiration time.
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The opinions expressed are mine and they are not to be taken as legal advice.