Loudspeakers - how best to prolong their lifetime?

Besides sunlight, smoke is something to best avoid. As is high humidity and moisture. Many speakers which have foam surrounds can easily have the surrounds replaced, it's not automatically a death sentence. And depending on the brand, it's probably best to replace the caps in the crossover every couple of decades or so. Large woofers should be rotated 180 degrees every couple of decades as well, if possible, to prevent stresses on the suspension.

Among my loudspeakers is a stock pair of 1977 Klipsch Cornwalls that sound excellent thirty-three years down the road. I have a pair of Pioneer CS-99A, with the cambric surrounds, from the same era in great condition. I also have some raw drivers from the 1950s that seem to work very well and friends that use Altecs from the early 1960s that sound pretty good.

Heck, there are guys using Western Electric and Klangfilm speakers from the silent motion picture era between the wars, and loving the hell out of them. I would not sweat it.

http://www.audioanthology.com/audio1.html

Materials do age and heavy use will cause wear and tear also. However, some speaker manufacturers have been supporting their original products for over thirty years. Meanwhile other speaker manufacturers role out new models and obsolete old ones every two or three years. There are countless numbers of flash in the pan speaker manufacturers that come and go each year.

Simply choose the right speaker company (the non disposable kind) and you won't have to worry for the next 30 years.

If you expect something to last more than thirty years without maintenance/repair then I think you are unrealistic.

Large woofers should be rotated 180 degrees every couple of decades as well, if possible, to prevent stresses on the suspension.

There are a lot of vintage speakers like Viridian mentioned that have doped surrounds.50s through 70s,and probably a lot of other years,I'm missing.These have a syrup looking type of coating on the surrounds to protect them,and keep them flexible.When that liquid sags toward the bottom,I was told to rotate them 180 degrees also.I'm not sure how often this needs to be done.Maybe going by looks,if it's sagging.Keep out of the sun like mentioned above.A lot of hard driving may age the glue holding the voice coil quicker. The foam surrounds could be changed like mentioned above also.With the foam surrounds,if you see the break/hole in them,don't use them.If you use them this way,you could damage the rest of the driver.If you catch it quick enough,they may just need new foam surrounds.The non-foam surrounds seem to keep on going,as long as they're not abused.

I was told to rotate them 180 degrees also.I'm not sure how often this needs to be done.Maybe going by looks,if it's sagging.Keep out of the sun like mentioned above.

It theory yes, but what if your wife refuses to go through with this?

I'm not touching that one.