An action to foreclose a mortgage is subject to a six-year statute of limitations, pursuant to CPLR 213[4]. The limitations period begins to run when the mortgagee or its predecessor elects to accelerate the mortgage. If the mortgage is payable in installments, the limitations period begins as to the entire debt.
DLJ Mtge. Capital, Inc. v. Hirsh, NY Slip Op 03505 (2d Dep't May 16, 2018)
Here is the decision.