Use a QuenchArc across the switch. It's a snubber cap that combines a resistor and capacitor together to suppress arcs on switch contacts. My good friend, who is a retired electrical engineer gave me a bunch of these several years ago and said to use them as it's the arc that damages the contacts. I've been using the switches on my Fisher items, one in particular several times a day and have had no failures yet so I'm guessing that the snubber cap is working. The ones he gave me combine a 220 ohm resistor and a .1 cap.
He said in certain cases they can be useful on items that "thump" when turned on/off as well.
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