Jim Redelfs wrote:

Given midwest weather, I am confident that we have had plenty of
transient spikes in the intervening years but I have experienced no
(apparent) damage.

During this time, my computer system has been ostensibly protected by a
strip-type surge suppressor:

http://apc.com/resource/include/techspec_index.cfm?base_sku=NET7T

I recently installed an Intermatic (whole-house) surge suppressor.

http://www.intermatic.com/Default.asp?action=prod&pid=339

I have been following the Intermatic thread with some interest.
Admittedly, it got a bit "deep" when the engineers began debating.
Still, I gathered much good information, not the least of which was that
MOV (metal oxide varistor) surge suppressors "wear out" over time - that
their efficacy diminishes with each surge.

Is it time to replace my strip-type suppressor? The LEDs indicate
nominal operation and protection, for whatever that's worth. TIA.

MOVs will continue to clamp surges until they fail. With high ratings,
readily available in some plug–in suppressors, they will likely never
fail - one reason some of them have protected equipment warrantees.

Should you replace your plug-in suppressor? Who knows. How old? Lot of
lightning storms? Suppressor turned on during a lot of storms? Short
branch circuit wire length to panel?

With your service panel suppressor, the plug-in suppressor should get
less action. I would probably keep it.

I would look for a UL 1449 *2nd edition* listing on the suppressor.
These are produced after about 1998.

The protected load can be connected (1) across the MOVs or (2) across
the incoming line. If connected across the MOVs, the protected load will
be disconnected if the MOVs fail and are disconnected. I believe new
suppressors are required to say if they are connected by method (2).
Added protection of connecting across the MOVs is another reason some
suppressors can have protected equipment warrantees. Unfortunately it is
not easy to tell which way a suppressor is connected.

All interconnected equipment needs to be connected to the same plug-in
suppressor or external connections, like phone wires, need to go through
the suppressor. If your computer is not connected this way you should
change the configuration. This is very important.

One of the suppressors I am using has a (total) rating of 1770J,
90.000A. It cost under $30 and has a protected equipment warrantee. I
don’t plan on ever replacing it.