Back in the dark ages when all engines ran points, the suggested interval was 10K miles or 6 months for daily drivers, whichever came first. Points that develop craters are a symptom of other problems- - - - -specifically, a bad condenser. Depending on whether it's over or under capacitance, metal will be transferred one direction or the other. I don't remember which way is which, but it's covered in most old-time service manuals. Since one point is slightly rounded and the other one is either flat, or has a hole in the middle, no matter how you choose to "file" points, it's a shade tree fix. Real mechanics seldom if ever did that, except in an emergency to get a stalled vehicle off the side of the toad and into a shop for a proper tune-up.
That hole was for "ventilation"- - - -supposedly to allow points to cool down during operation and prevent burning. It was mostly a P.T. Barnum sucker bait move that just made it difficult to set the gap accurately. Of course, the pros used a dwell meter and left the feeler gauge in the tool box.
Jerry
