I've got the original plug in my 12yr/old Honda GC powered push mower and my 12yr/old Tecumseh OHV snowblower and they run fine. I tend to leave them 'till they pose a problem.
I assume your 2165 has a Kohler Command? I dunno if Commands have a tendency to do this, but some aluminum heads will strip out when you try to remove real hi mileage/hour/age plugs.
For that matter you might atleast want to pull and put a dab of never-seize on the plug threads.
Joel