Speaker life expectancy: How long can you buy used


I'm in the process of assembling a cost-effective second system with high quality used or demo gear for use in a relatively small room (appr. 20qm, normal height, wardrobe, big window, carpet, sofa, apart from the size of the window quite average really).
I saw a pair of Avalon Monitors, that I think could fit the bill at 30% of the original price, mint by the looks of them BUT seven years old! In spite of the good things I hear about Avalon's longevity, I do wonder whether it is wise to buy a seven year used speaker, any speaker.
Apart from considerations of wear, where would you draw the line that even a steeply discounted speaker of justified fame in its own time will likely not be able to compete anymore with new products that may cost just about the same amount of money, new that is. And are there exceptions to the rule?
Any considerations or experience you may want to share?
Karel
karelfd
Oops! My EV Patricians are 40 years old (not 30 as I indicated). They are from ther late 60's. And, again, they still sound great.
30% off does not seem like a good discount on used speakers, but if that is the "market rate"....
I recently purchased a pair of Infinity RSIIIBs from 1985 and they sound amazing. I have heard many medium to high end speakers such as Paradigm, Sonus Farber, B&W, etc prior to purchasing this vintage set and although all of them sounded good, to me, for the thousands they cost they simply could not beat my Infinity's when concidering sound and cost.
Audiofeil states:

"I suspect that years alone is a poor measuring tool.

I would guess hours of use, how the speakers were driven, and temperature/humidity conditions are more important determinants"

I agree. Very important criteria.