Thoughts on extending speaker life.

@daveyf --

For those with other types of driver design, what are your concerns about the extended usage of this kind of driver as it ages?

I’m not concerned, really, but I’m invested in this subject nonetheless. My speakers are all-horn loaded using compression drivers for the midrange and tweeter, and a (hidden) 15" bass driver with treated accordion cloth surround in a folded horn. None of these drivers are directly visible (only the exit area of the compression drivers via fine-masked grilles), and so their diaphragms and surrounds aren’t exposed to light - not even the bass driver, which is situated behind a some 3x13" slot (its exit area into the folded horn). Treated cloth surrounds at the end of paper cones, even when exposed to light, usually last decades, and the Mylar and paper composite material of the tweeter and midrange drivers respectively should have close to indefinite lifespan. All things considered (including cross-over components, cabinetry, etc.) I would expect my speakers to perform immaculately (way) past 30 years, quite comfortably.

If anything it seems to me regular use of one’s speakers is the best way to actually preserve them, and in your specific case I wouldn’t worry about the rubber surround of the of bass/midrange driver. Try to avoid them being exposed to direct sunlight, and with rather normal atmospheric conditions, humidity and no severe temperature variations (other than what normally occurs when opening windows and such), I gather you should have decades of trouble-free service from your beautifully crafted, well-engineered and high-quality speakers.

An occasional application of Armor All is beneficial for surrounds.

I would never apply anything to my speaker surrounds. It can do more damage than good. As long as you keep your speakers from exposure to any of the known things that can cause degradation of the surrounds, the surrounds should last a lifetime. The things to avoid are UV (from sunlight and fluorescent lighting), Ozone (laser printers are big culprits), VOCs (from paint, household cleaners, furniture polish, metal cleaners and of course cigarette smoke) and excessive heat and humidity.

I purchased my KEF Calinda speakers in 1979 and they are still going strong in my third system. The surrounds are rubber and still look like the day I purchased them after 40 years. My KEF 104/2 speakers were purchased in 1991. They are the biwire version and have foam surrounds and foam donuts on the woofers. After 28 years they still look like new and show no signs of degradation.

Don’t forget about the Most important part of the speakers,
the Heart ,the Crossover , Parts Quality is average at best 
on 90% of all crossovers, upgrade withsame values just much 
higher quality  parts ,including , wiring, and getrid of the cheap gold plated brass that most speakers connectors have as well as your electronics rca and Loudspeaker terminals ,that alone a very noticable sonic improvement.

AR 18S surrounds crumbled after maybe 10 years. Mission 761i will be 25 (years) in a month or so. surrounds look like new. Third pair, 14 years, looks like new, too. Fourth is still too young to tell. None of them has ever been treated or paid any attention to.

Could it be that something about materials used has improved over the last 20-30 years?

I would not apply anything on surrounds. There is more chance I would damage them, poke the hole or something else disastrous, than that I would extend their lifespan by a few more weeks. I do not think it is worth it.