[dB Cooper]

Is it good as long as the 'protected' light is on or should they be replaced periodically regardless of whether they've been 'spiked' (ie, do they lose effectiveness over time)? I know there are a lot of members with EE backgrounds so I just thought I'd ask.

[Armaegis]

Most cheap consumer brand surge protectors do in fact "wear out" over time. They have an "energy" rating which is how much surge energy they can absorb before they no longer do their job. Unfortunately, there's usually no way to tell how much protection is left. Some newer surge bars have limiters/indicators built in that may indicate when they're no longer good.

Decent article here:
https://www.cnet.com/news/9-things-you-should-know-about-surge-protectors/
http://thewirecutter.com/reviews/best-surge-protector/

Now moving up to audiophile stuff... well it varies wildly. Some can wear out, some utilize devices/methods that don't. Personally, I would stick with established industrial brands like Furman, SurgeX, ZeroSurge or Brickwall.

[Folsom]

SurgeX, ZerosSurge, and Brickwall won't wear out, short of continually lightening strikes for awhile.

Regular units with MOV's are a gamble.

[Speedskater]

a] Whole home surge protectors at the main breaker panel are the best plan. They should have an indicator.

b] SurgeX, ZerosSurge, and Brickwall point of use surge protectors are excellent but extremely expensive.

c] Other budget point of use surge protectors, may not be needed, may not work when needed, may dump noise onto the Safety Ground.

d] There are now many surge protectors in a typical home adding another may not matter.

e] If there is more than one budget surge protector in your audio system they should all be the same brand, model and mfg. date.
(you want them all to limit at the same voltage)

[mikeeastman]

Midnight Solar make a very good surge protector that has a LED that indicates if it is working and when it has absorbed all the surge it can handle it has a replaceable part to bring it back to full protection. They list for about $120 but you can pick them up for about $90 at this site
https://www.solar-electric.com/catalogsearch/result/?q=surge+protector.

[Folsom]

$100 or so on eBay will get you a lightly used SurgeX. And if budget allows then the ZenWaveAudio version is much, much better.