Why are older tubes so much sought after

Let me try again!

Trelja- Just curious what 7199's you're using. I owned(and modded) an ST-70 for about 15 years and found the Sylvania and Phillips ECGs to be the best. Have you installed a NOS 5AR4 yet? Talk about another revelation! I used a Mullard in that position. Regarding the others' experiences with their un-named NOS tubes of unknown origin: (like everything else in this hobby) Your results will depend a lot on into what these tubes are plugged, their condition/quality, and who is doing the listening(many variables). The best NOS tubes just get out of the way of the music and add or subtract nothing, which is the definition of, "transparency", and you've removed one variable by using them. From there it becomes a matter of taste and/or what may be lacking in the rest of the gear.

Well Albert,the movies,music and entertainers of the 40's,50's,and 60's might have to be included as well -:)

Mil Spec components were usually required to be much better than necessary. That was before cost control became important. Nowadays most military equipment uses commercial hardware whenever possible, which greatly reduces cost, improves (yes) reliability and performance. Also, we have learned to make electronics whose performance is derived from the basic circuit design rather than from reliance on tightly spec'd components and trim procedures.

I am surprised that new tubes are less accurately made. A tube would seem made to order for precision automated fabrication.

I wonder what will happen when all of the nos tubes are gone? and no one will have to pay the outrageous prices folks are charging for them. Will highend audio survive?
What will we do? Lord help us!
Somewhere in this scenario sanity has taken a long vacation but again, we're talking about highend audio where some would say sanity has no place.