If you had a dozen pairs of classic vintage ubes in your closet

@vegasears I hear you but you can only demo so many allegedly "better" pre-amps and amplifiers at very significant cost levels, and watch dealers leave with the tail between the proverbial legs before you decide maybe expensive NOS tubes are a pretty good way to go. Some vintage gear just simply kicks axx when in a well matched system. Last demo pre was an Audio Research LS 27 and tube guys just don’t or won’t haul 70 pound amps in here anymore for a room full of guys to agree the SS amps were better tonally and detail wise. I just installed half my remaining NOS Siemens and Halske Cca 6922 grey plates (1962 issue). I see a pair for sale at $2K. I used to buy them for $40 each.... maybe 10 years ago I sold some for $200 each.. I should have kept them.    Replacing a vintage pre with a new $16K (or more) unit is not a solution to not buying NOS tubes.

You do realize that all tubes are aging during every minute that you are using them, do you not? So, you can pay hundreds or thousands of dollars for tubes that may sound wonderful on day one. That is a best case scenario, because in many cases inexpensive tubes will sound better than these rare NOS tubes that cost a great deal of money. But let’s assume that The expensive tube does sound great. From that moment forward it is decaying. Eventually your investment will fizzle out. You can get much more bang for the buck, if you learn how to solder, and how to read a schematic, and upgrade coupling capacitors for example in your gear. That sort of change is permanent and never goes away. Capacitors make a far larger difference to overall sound quality than do tubes.

Furthermore, when you do pay big bucks for a tube and install it, you are then very biased toward hearing an improvement. None of us is free from that listener bias. You have spent the money, so it must’ve done a lot of good. Get your wife or someone who doesn’t know what you did to have a listen, before you get wild over a boutique vacuum tube.

That's for sharing that lewm...   is that really true, my tubes are aging when I use them? when the heaters run?  Since "in many cases" why don't you find me some inexpensive tubes that outperform Siemens & Halske Cca 6922 grey plates circa 1962 or 1975 SSW 6N23P Reflectors.  I'll get out the soldering gun I've had for 40 years and ask it if I know how to use it, the iron I used 60 years ago is long gone.  The Heathkit multimeter I built 55 years ago finally gave up, who would think you could buy one for $14 bucks and have it delivered tomorrow. I don't agree with you on caps over tubes in my system and my wife does concur with my findings.  Perhaps you are biased in your listening, I'm not, very engineer based analytical. What works for you may not be for everyone. 

For all my tube equipment, I always purchase two identical sets of tubes.  One set is for every day use and one set is used as a reference.   Over a period of time audio neurosis sets in and I begin to doubt the tube’s performance/lifespan.  That is when in pull out my reference set and compare them to the everyday set.  If all is good, I merely put the old set back in and enjoy until Audio neurosis strikes again.  

I'm using those very same S&H tubes in my Manley Steelhead.  And this will killya:  They were given to me by a friend who converted to solid state.  Don't ask me if I like them, because I am biased to love them, now that you told me how much they could be worth.

You wrote, "Perhaps you are biased in your listening, I'm not, very engineer based analytical."  What about this exchange of ideas would support that idea? It's a scientific fact that we as humans harbor subconscious biases that affect what we see and hear, no matter how hard we may try to be neutral or "analytical". Spending big bucks on a tube would tend to enforce a very conscious bias in favor of that tube. This is why science that reports human behavior or relies upon it always has to include enough subjects to ameliorate the bias effect and preferably be conducted in a blinded or double-blinded fashion.  I am sure you know this, and that is all I was trying to say.  You could be analytical as a single observer, if you are making measurements with a reliable instrument.  But since this is all about opinions, there is no avoiding bias.