How long do high quality speakers "last"

mshan  How long do high quality speakers "last"

First off you have, one of the nicest sounding semi bookshelf's in the Response 2. And they still demand good money even today.
 
Foam roll surrounds are the best, but do rot and should only be replaced with exact same ones. As the "compliance" of the roll surround is part of the Thiel & Small parameters that has dictated your box and port size to that base driver.

I would also every 5 or so years, rotate the bass driver 180 degrees, as the cone/roll surround will sag unevenly and could eventually cause what's called "polling", this is where the voice coil is no longer in exact center of the magnet gap and starts to touch/scrape it.

Cheers George       

One nice thing about my ZU's is that you can purchase upgraded drivers. I purchased my Omen Defs in 2012 (update B) and they have the updated tweeter. Since, ZU has released upgraded larger drivers as well. Outside a light dusting every now and then, the drivers look and feel as good as new with no deterioration (at least from what I see or hear).

mshan, it is extraordinarily variable. Foam surrounds are always a bad sign and these hardly ever make it past 25 years. Voice coils can burn out or unravel and the driver starts making strange noises. On the other hand I have two pairs of Mirage speakers in my workshop in the worse of conditions. They are 30 years old and sound fine although they don't look so hot. A good ESL like a Sound Labs speaker will last indefinitely.  

My Thiel CS2's are 32 years old and still mint. They may outlast me.