How long do good speakers last?

I've owed apogee divas with the active Dax for 30 years. They perform beautifully. About 7 years ago I developed a frequency-specific buzz along the top edge of a woofer ribbon. I decided to go with Graz ribbons for both speakers,  along with a complete refurbishment of guts and wires by Bill Thalman at Music Tech in VA. He does a fabulous job - the speakers retained all their quality characteristics, with more extended bass, and dynamic range. Timbers and imaging is second to none. Bottom line, it was the best value decision I've made, rather than purchase something more expensive with inferior musicality. Believe me- I checked out many replacement options!! It is worth buying the best you can and maintaining them. New front end equipment (Rossini DAC, D'Agostino amps, ARC preamp) has improved the sound substantially and impressively - old speakers do more that "keep up" - they expose improvements and deficiencies truthfully. Everything needs maintenance or repair occasionally but can last many years of frequent use. In my 60s now I hope to keep these till I give out, hopefully decades from now. If I need to downsize I will very reluctantly, but it would be at the loss of my beloved Divas! Hope this perspective helps.

My Acoustat 1+1's electrostatics are doing quite well, thank you for asking. I had to refoam the RH Labs sub but it also is doing well. Call it 30+ years for all of them... so far!
I have to go retrieve my dad's B&W Matrix 800's... I'm HOPING they'll be okay as they've gotten very little use in 20 years. *fingers crossed*
Happy listening.

There are 3 variables affecting aging: 1) Materials and manufacturing quality (or lack thereof) used including glues, ferrofluids, foam surrounds, etc. which can age over time. 2) Environmental conditions including temperature and more important humidity along with potential detrimental lighting effects (UV).  and 3) Damage based on usage = high SPLs that may damage driver coils and / or crossover components.

Late 80's B&W 801 matrix 2 which, aside from replacing grill fabric due to original owner's music loving cat, have required zero maintenance in over 30 years.  I keep the fabric on to prevent UV damage as the room has natural light.

I have a pair of sonus faber Guarneri homage, circa 1999, still in perfect condition. However, SF speakers require some yearly maintenance. The leather will fade if not conditioned properly & the wood needs TLC to. I would contact SF & get their maintenance suggestions. The leather will have issues if not maintained properly, fading and potential cracking. I leave mine covered when not in use to protect the wood.