Thanks. I've tested with one of those, and it doesn't show any faults. But I don't know if it's still able to absorb a surge, or if it could create a hazard if it tries to.Klein Tools RT110 Receptacle Tester detects the most common wiring problems in standard receptacles. Conditions indicated: wiring correct, open ground, reverse electrical outlet, open hot, open neutral,www.homedepot.com
One of these Receptacle testers will easily and safely let you know if they have developed a fault.
You also can get a fancier version that shows voltage as well as faults plus tests GFCI outlets. Either is available at big box hardware stores as well as online.
The RT250 is an electrical receptacle tester that tests the wiring conditions at an electrical outlet and inspects ground fault circuit interupter (GFCI) devices. The LCD displays the voltage, identifieswww.homedepot.com
This of course doesn't tell you how they are designed. So checking them periodically would be a good idea if you keep them.
I don't know if it's significant that the light in the power switch flickers like a dying neon sign in a film-noir hotel window.
I wrote to the manufacturer and haven't heard back. Curiously, they give a lifetime warranty with these.