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

@jjss49 ,,,  r  u  thinking your English language punctuation and usage of upper and lower case characters is correct?  Perhaps you should use spell check and re-read what you are posting.

A bell just went off Elliott....   we had numerous discussions on the dpreview website if I recall properly.

@lewm.....   you have a point.  My ears have told me when it is time to change for the last three decades.
@pindac     ..  there was a time when NOS meant New Old Stock, not that the tube still reads close to new.  I'm talking perfect old lettering and pins that look like New Old Stock + a tube test.

Elliott... you have a good point about the tube tester. There used to be one at a repair shop in Miami but he closed many years ago and I have not been able to find anyone with one. I use 6DJ8/6922 tubes. About 15 or so years ago I rolled everything I could get my hands on from all over the world. Bugle Boys/Amperex/Valvo/Chinese 6DJ8s/Telefunkens and many more. Discovered that the Siemens and Halske Cca 6922 Grey Plates round and D getters from the later 50’s and early 60’s were the best in my system, except for a stray set of 1958 Valvo Pinched Waist 6922 Cca tubes. Found a source in Germany and stocked up on the Siemens... they were about $40 each back then. Sold off a bunch at $200 each and still have a couple I just found in the back of the closet. I see someone trying to sell a matched pair @ $2000. Probably try the ones I have today. Currently I’m using 1975 6N23P SSW Russian Reflectors I get from a lady in the Ukraine and have watched them double and a half in the last few years. Have a couple of Russian Rockets in the closet too I didn’t like as much as the Reflectors.
Generally I’ll just run them until the bass or highs start to deteriorate and then replace them. I really like the tester idea.. want to keep my 30 year old pre-amp going as long as possible.   https://www.martindareff.com/Other/HDR-Treated-Images/i-ZmLg23s/A

@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.

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. 

That’s all well founded lewm.... and I am making measurements with my reliable instrument, my ears..... which is what it is all about isn’t it? I had the wife listen to the S&H’s and some SSW 1975 Reflectors I have a small stock of and we agreed completely on what we heard. The S&H get the nod on vocals but the Reflectors simply play more music with greater detail, especially bottom end bass with stringed instruments such as bass fiddle.. Since I can't get any more S&H’s I ordered the last matched pair of 1975 SSW Reflectors my source had and a couple of 1977 Rockets as well. Should be well set now, at least until we finalize the digital cable from the streamer to the DAC.