[Steve]

Seems to me that if one wished to "improve" upon the metals used within a vacuum tube, that one would subject them to cryogenic treatments before inserting them into a glass envelop.  Treating the many different materials within a vacuum tube afterward by subjecting the entire tube to ultra cold temperatures seems like snake oil to me.  The article linked below asks why a company like Mullard, who possessed all of the facilities to cryo tube materials and who had good reason to build very long-lasting tubes for critical military usage, never cryo'ed tubes. 

https://blog.thetubestore.com/cryogenic-treatment-of-tubes-an-engineers-perspective/

I will add that I've never purchased a cryo'ed tube.  I've conducted many comparisons over the years of cables, tubes, DACs, preamps, amps, etc., but the whole cryo thing seems so farfetched that I've never bothered.

The article is questionable. Cryogenic treatment does "relax" the molecular structure,
does minimize stresses, and does actually reduce resonances/"ringing" of materials.
Personally, I have not found it takes a long time to "break  in" a cryod tube.
 
Industry has been applying stress relief and relieving "ringing"/decayed oscillations for decades.
Not understanding the circumstances surrounding Mullard, and using speculation about Mullard
can lead to many erroneous type of conclusions.

As far as cryogenically treating after assembling a tube as being "snake oil", doing so after tube assembly
is a good test of integrity of the tube structure. The internal parts get cooled as they should. I have
cryogenically treated tubes sitting here for decades without one failure. I hope this information helps
you and others in understanding.

cheers

steve 

[Armaegis]

Speaking as an actual metallurgical engineer... I'm not gonna say anything about that at all since that wasn't the question.

Speaking as a math teacher... a sample size of two is not what I would call adequate data from which to draw a trend 

[Elizabeth]

I also apologize for over reacting. I should have recognized the joking side of the post, instead of just jumping up and down mad. 

[Armaegis]

Geez, and here I was just trying to bring some levity to what looked like was becoming a metals argument. No harm or belittling was meant by my comment, though it seems I made a very poor attempt at humour so I apologize for that. I've always thought you were one of the more even handed of the members here, as you don't typically call people out and simply state your preferences.

But honestly, I think two data points is more easily attributed to coincidence rather than a trend due to cryo.

[Steve]

Please delete this post. My apologies.

[Armaegis]

I tried to make a lighthearted joke.
Clearly it backfired.
I got called a jackass and I made a kneejerk defensive post about it.
That's all folks.