How long does it take a decent quality speaker to "wear out"?

The ears usually wear out before the speakers do. Given some sonic degradation over time, it is likely so gradual to even be noticed, if at all, or subject to the “used to it” effect.  Playing or swapping out will produce sonic differences. Is the result an actual improvement? Only your hairdresser knows for sure. Exhibit A, most of this forum is dedicated to sonic perceptions 🙃

Totem Acoustic Speakers are made to last a lifetime. In addition they are designed to sound identical in any part of the world they are domiciled. They are absent of any wool or Acoustic filling that breaks down over time. 

@immatthewj 

Good question!

Other than the driver surrounds crumbling, I have never had a speaker “Wear out” I have upgraded crossovers because it was an upgrade, not because of any other reasons.

@immatthewj 

Correction,  I did have to replace a tweeter, but that was probably my fault. 😀

I had to have the foam surrounds of my WATT/Puppy Puppies replaced after about 20 years.

Long time ago, I blew out the midrange of a Rectilinear III Highboy doing stereo wars in a dorm.  Duh.