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

Think you are OK with the B&W for now+++ as they used good poly caps and wirewound resistors in their crossovers (you have already addressed the driver materials used).

How did you end up with good rectifier tubes for the Cary preamp?

DeKay

@dekay  , thanks for asking.  Well, I went on a used 5AR4 buying binge of sorts --a UK Amperex, a Holland Amperex, and a Hitachi/(Matsushita?); and I have a Gold Lion I bought prior to that and the original Sovtec, so if nothing else, (given my age) I hopefully have a life time supply.  

But of the three used tubes I bought I have only got around to running the UK Amperex, and I am liking the way everything is sounding for me right now.

But the thing is, I had the Gold Lion in before I put the UK Amperex in, and I thought it sound good with that and I never felt any sense of sonic revelation when I swapped it out.  And the same applies to the Sovtec that I swapped out.

I hate to say it, but maybe I don't have the ears for this. 

I have a pair of Thiel CS 3.7s from 2011 that should last forever, i take really good care of them no sun light and the drivers are all aluminum.

Might only upgrade the crossovers one day with top of the line Mundorf caps.

I already upgraded the binding posts with Mudorf versions.

My Acoustic Research AR-9 from 1979 still sound great  all original parts 

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.