Depends a lot on the usage and the environment. A lot of my gear that has always been in the house and under climate control has lasted 37+ years so far with only minor service, not due simply to age. A few caps in amps and some speaker drivers have been replaced, but very few issues. Some items that were kept in the garage did not fare as well. Foam coming apart, cabinets deteriorating, oxidation on the electronics internals, etc. I have friends that bought cheaper stuff and it was a total loss in a few years. Hard to say how long they last but buying good quality helps things last longer.
How long does it take a decent quality speaker to "wear out"?
After all, they do have moving parts and capacitors. . . .
(I suppose that "decent quality" s a relative term. FTR, I am running a pair of the older B&W 805s, and for all I know, they may not actually meet the criteria of "decent quality.")