How long do good speakers last?

AllIison CD8s, 1988. Refoamed this year. Will never give them up.
Mirage M290s, 1995, still perfect.
Audio Physic from 2001, perfect. Still think of them as new.
Tannoy near fields from early 90s. Never needed work. Perfect.

If you are 51, the only issue you will ever have is if you want to get something else. Those will last until you are playing dominoes in the old folks home. Where I'll be soon with my Allisons.

My DQ10's still sound wonderful.  All original except a re-foam.  They could be 40 yo......

have a pair of realistic nova 6 speakers dating from 1971. they still work as designed. a pair of magnapans from 1982, they still work as designed. a pair of thiel cs.5 speakers from the late 90s that still work as designed. newest ones are a pair of vandersteen 1ci speakers that are only a few years old. 

I bought my Tannoy 638’s when I was in the Navy in 1994 on a port visit in Dubai. They are still perfect, though I have replaced a blown tweeter once. 

@oldhvymec....Wow.....

"Infinity InfiniTesimal RS 0.1. 1978 I have 2 pairs...."

I remember listening to a pair of them and thinking:
 "..these would be spectacular in 2 pairs....and a correctly sized sub..."

Did you?  Do you now?  Just curious...;)