How long should high quality speakers last?

Speakers are made up of various materials and devices. I’ve found that the moisture content of a component is a big factor. As components dry out things happen such as materials turning to dust, convert from solid to goo, leak, or become brittle. Foam, plastics, coatings, capacitors, etc. We just serviced a pair of 64-year-old speakers. 5 of the 6 drivers, AND the crossover components were still operational. Not sure if the "blown" tweeter was due to abuse, or aging in this case. I’ve got a single Klipschorn from 1958 in the loft what works fine, with the correct drivers intact. I don’t know the complete history of the speakers.

My hand-built speakers are made up of 24 drivers (rubber surround mid/woofers, soft dome tweeters). I had them when I met my current wife 34 years ago. The speakers (and marriage) are hanging in there.

In my speaker rotation are a pair of 37 year old ProAc Studio 3. I just replaced the 2 electrolytic caps in each crossover. One was bulging. 

While State Farm insurance is no authority on matters concerning audio gear they do assign a life beyond which there is no depreciation applied beyond a certain age and that number is 10 years. This might be useful information to someone here and I offer it up in the hopes that it’s useful 

I have several speakers that I liked over the years which I have kept and still using regularly. For example, B&W 801 Matrix S3, German Physiks Unicorn II and Borderland iV, Wilson Audio WP7, all over or 20 years old. I have a 3-way KEF that I bought as a student 40 years ago and still plays as new. All in original condition. Therefore they can last, if you take care of them and are held at appropriate conditions. Personally, I avoid upgrades, unless not functioning, which has not happened yet.

I bought a pair of JBL L-65's new in 1979. Refoamed in 1989. Refoamed again, crossovers rebuilt, and grille fabric replaced in 2023. They sound better than new now.