How long do B&W 800 series speakers last

Hi,

I am curious to know the average life of these high end speakers particularly B&W800 series. Does the surround/ cone material give up with time due to material fatigue, dust and air corrosion etc
Does the SQ degrade.

I assume they last for like 20-30 yrs given the resale prices. I see prices dip to only 50% in 15yrs. Even less for N805's

I am sure 6-7 yrs use is very normal But what about 10-14 yr old nautilus ?
Or how about an matrix 805 treated like a baby for 20 yrs.