Buying a 10 years old loudspeaker

Just like with 10 year old cars, you have to take it on a case by case basis. One owner is a good sign. There are forty year old speakers that have been in the same room their entire lives and three year old units that have shipped cross country 4 times already.
The best advice above is to consider the seller as a strong indicator of what you are buying.

What are you looking at?

My JSE's are from 1986 and still perform flawlessly, I think if the tweets aren't damaged and the surrounds are OK, you are fine buying old speakers.

Replacement drivers are my only worry when I buy old speakers.

My speakers are 16 years old, and I know they will need some amount of repair some day...but the parts are there, so I don't worry about it.

Dave

Dave is right. Parts are key, considering many higher end designs (especially over the last 10-15 years) were designed with proprietary drivers. If these companies fail accessing the oem parts is a crap shoot at best.

...more My Speakers are...

My kef 104s were new in 1978. i replaced the tweeters in 1989.

My rogers studio ones were purchased in london in 1986.

They look brand new and sound like a well aged martin guitar.