Why aren't new vacuum tubes as good as old ones?

I had a sloppily made Psvane pair that I sent back, but that was cosmetic really (on one tube) and it was a matched pair...they did seem to sound OK. The next pair was better, and have remained in their sockets. I wonder what the number of bad 120s is relative to others at ARC, as there hasn't been much reporting of 120 failures otherwise, or at least from what I found in my research (research...ha...more like "lazily poking around").

Is it fact, or hype?

It's fype.

What is the definition of "good"? Sonic quality? Durability? Given the longevitiy of some tubes (300b comes to mind) and unless a tube fails "early," it will be hard to prove that new tubes are predictably shorter-lived compared to older ones. Or am I wrong?

Click HERE to view the Mullard video. This is really fascinating.....Worth a look.