How long should high quality speakers last?

Jeff Days’ vintage office system:

These are heavy loudspeakers, somewhere in the 250 pound range each as a guesstimate. These vintage loudspeakers—like me, are over six decades old now—have accumulated a few scuffs and scrapes over the years, but still they are in very nice cosmetic condition overall considering their age, and the drivers, horns, crossovers and cabinets are in essentially perfect operational condition—a testimony to the impeccable quality of Altec products from that period.

My speakers are 45 years old. The woofers were refoamed 10-15 years ago. Otherwise, they have been perfectly reliable since I bought them, and they sound great.

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