Guidelines for buying used speakers (as in, are there any?)

Age or the amount of owners are irrelevant condition is whats important as were pointed out.

Depending how old speakers are original foam surrounds can be a concern.  As can replacement surrounds depending on replacements, were they done with quality accurate duplicates made by a company for a specific driver or one size fits all flea market type surrounds. And were the replacements installed by somone reputable or atleast someone that cared enough to do a good propet job. This should reflect in asking price or make or break the sale.

Also wire coatings can dry out and become brittle and crack over time and cause a short in extreme cases.

Capacitor age might also be a concern, they dry out in time as well, some sooner than others. Poly caps tend to last longer.

None of these should become a concern unless reaching over a decade plus. Or depending on where the speaker lived its life thus far. Sunlight and tempatures can play some part in it.

Modern foams supposedly outlast the older ones. Its a bit of a head scratcher. Who’s to know exactly what speakers employ the "new surround" technology.

I have speakers that are 20 years old with foams that are still holding up. UV from sun and artificial light and the gassing of of carpet and other materials will play a role in there longevity.

Arro's are fine sounding speakers in an appropriate size room with good amplification while standing at an optimum distance from wall. I can see some people being able to live with there bass response. I preferred mine with a pair of subs. But I like to feel the bass as well as hear it.