I'm not sure about tweeters in my Hyperions HPS-938 but midrange uses ferrofluid for suspension. Ferrofluid dries over time and has to be replaced but I don't know if it is 10-20 or 30-40 years. Also, some speakers have electrolytic caps in xover but it should last perhaps 40 years in room temperature.
Will the sound quality deminish over the years?
I bought a set of used B&W 802N and see a lot of nice speakers for sale here. I wondered if the age of the speaker would cause the sound to degrade. Sure, I have heard people state how great their 40 yo speakers sound, but could that be like shocks on a car? You won't notice how much less they are until it is changed.Just a curious thought as to 10 - 20 years down the road, can I expect the speakers to sound as good, especially when laying out a lot of quag.