I once had a Briggs & Stratton motor that outlasted two lawn mowers. When I found the motor, it was still attached to its original mower, but was sitting on the ground because the mower had rusted through. A friend had a Craftsman mower that wouldn't start, so I put the B&S on it and mowed for several years, including clearing a bunch of brush. I used it like a miniature bush hog. That mower bit the dust when one of its corners refused to be repaired anymore (I didn't know how to weld then), so I put the motor on a third mower. It was still running great when I gave it away. I should have kept it.

A thirty-one year-old Toro is impressive, by the way. You must have taken good care of it.