Simple question…
Bonus question: If your speaker still plays, surrounds still intact… appears fine… How does it measure after: 1 Year? 5 years? 10 years? 25 years ?
Bonus question 2: How durable is sound quality in a speaker over time?
Paul: Those Infinities… how did they wear? Sound evolve?
Peace
Bruce in Philly
Dome tweeters with ferrofluid, foam surrounds, rubber surrounds, damping goop covered boards, capacitors, even resistors (esp if running hot) and for all I know some enamel on inductor wires, all wear out.
Oh and wood changes over time, and particle board can degrade over time.
I have several pairs here, featuring issues with some of the above at one point or another.
My oldest pair is circa 1970, using 1960s tech. Hence no rubber, foam, ferrofluid, etc.
So drivers appear to be good as new. Crossover replaced entirely with new components (same design).
The chipboard of the case is a bit iffy in one or two places (though still maintaining structural integrity so far with a bit of help and injected glue).
At some point I’ll have to give up on them though.
Apologies for not directly answering your questions, it’s late here 
I had a pair of Kef 105/3. At 20 years old the surrounds on the woofers deteriorated to the point they needed to be replaced. I had them professionally redone by Regnar in New York. They did a fantastic job. I will say the woofers had to go through a break in period again after the rebuild.
The manufacturer of my speakers clearly states in their specs that the life expectancy of the speakers is 100 years.
And I do believe that my measurement tools are aging ahead of the speakers, so they still sound great as time passes----sort of like when I played in bars—the drunker you get, the better we sound—so drink up.
I do not expect to be around in 20 or so years, and even if I do, warranty on my ears would have expired 
I have had to replace the foam surrounds in the 12" woofers of my very old AR-58’s. I then had to replace the midrange driver as that surround dried out. I replaced it as the surround was very small and I was able to find an Audax unit with the same basket size and hole pattern, the same efficiency and ohms rating. It was also a sealed back unit which helped clean up the midrange some. They still sound very good to me. but at nearly 74 I’m not sure THAT is a good thing. lol
I should be replacing them, but I love recording and just bought more mics instead.
Naw Serhan…just go to the Maker and get some new ones !!!
I still recall my answer to the how many speakers have I owned thread. More than I can remember. As a diversion to responding to the query I’ll just point out I’ve never owned a pair long enough for the surrounds to wear out, the ferrofluid to dry out, etc.
I think having speakers perform better than you ears is a good thing.
Fair enough! I will schedule my speakers for the bench test to coincide with my hearing checkup.
Like everything else, speakers wear out. How soon they wear out depends on the quality of the materials used, usage, and placement. Direct sunlight is brutal on cone speaker surrounds. Usually these are what deteriorate on cone speakers. When I first heard my friend’s vintage JBL L160 Horizons running with his McIntosh separates, the surrounds were deteriorated and they had no bass, just rattle. After he had them re-coned they sounded very different. More what they used to sound he said. When his Velodyne subwoofer started to die, I thought the cone was detaching from the back (the voice coil?). The rattling got worse to the point it wasn’t worth listening to.
Panels are interesting. Eventually mylar panels separate from the grid and they start to rattle. I heard this on Sound Labs A3’s. If you push them too hard, the current will “arc” and the mylar will fuse to the wire grid. This happened to my friend who owned Quad ESL63’s. I think they stopped playing. Both of these need the panels to be sent back to the factory to have corrected. For the Quads he had to make sure he had proper boxes and they had to be fastened to a pallet and shipped to England.
Usually when the speaker is going bad, it’s audible. The owner will tell that they don’t sound right.