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

Read seller feedback most important. Don't buy from someone unproven as a seller unless local pickup is an option. 

Your guidelines might be okay starting point, but plenty older than 5yrs that would be great buys and last many years without incident. There are also plenty that have had 2 owners that would be great. Find a model you like a lot, and then ask many questions and be pragmatic. 

Considering all the time online researching, etc. vs. a few hour drive to demo/pickup, sometimes it's worthwhile investment to take a nice long drive. Cheers,
Spencer

Price to condition, that is all.

jimspov-

Back in January of this year, I scored a sweet pair of Thiel speakers that I have been wanting to purchase for many years.  Always, inquire about the number of owners. Next, inquire about how the speakers have been stored and treated ( not in a garage, unfinished basement, storage facility) for example.  Finally, whom is selling- a fast buck, professional find-and-sell or a Music lover/Audiophile?

I am very fortunate, as my speakers, were (2) owners. The 1st was a dealer/retailer. 2nd is an Audiophile with an impressive dedicated listening room. In other words, these speakers rec eived the very best care, conditions with all original documentation.