Cagey,
Thank you very much. This is an absolutely GREAT explanation to all of us who don't understand much about electricity! Shortly after I built my home, a developer down the road came and began digging along our street. Despite lines being marked for them they hit a main line and sent a surge SO big back into several homes, mine included - less than a year old, that it burned EVERY outlet, light, appliance...........everything that was plugged in and black smears out of unused outlets. Over 20,000 in damage. Fire department, new paint all smeared with soot...no A/C (blown out)....all appliances...blown out. On top of that, NO ONE, not the developer / digger (who claimed the county's marks were sprayed incorrectly), the developer who hired the digger, the electric company,........no one wanted to take any blame for the incident. I had over $20,000 in damages - nor to mention days in 90 plus degree heat with no a/c, no stove or oven or microwave, a house that smelled like smoke for a month. I learned a LOT about electricity at that time. Even the most expensive of these surge protectors wouldn't have save us from what happened. We didn't get a jolt, we got many thousands of amps blown backwards. The sorry part was that it took over a year to collect and, of course, we had to immediately bear the cost while waiting....and they preferred to negotiate into desperation for us homeowners.
Accidents and these spikes in power are actually common, especially in places that see storms with lightening that occur with some frequency. Everyone needs to protect everything they own BEFORE the incident. That's why I was looking 3 weeks out.
I have saved this article. From most of the research I've seen, most units do have shelf life (several years is when I see people saying their units from varying manufacturers begin to show problems). New items are being developed every year so plan to keep abreast of new technology!
Thanks again!