? Tube Replacement Question ?

One of the problems with tubes is once your start "thinking" that it might be time to change the tubes, your doomed, you might as well change them out because in the back of your mind, you will be always questioning the tube's performance, even if they are 100% good.

Something VERY important, when purchasing preamp tubes; being CERTAIN they are CERTIFIED LOW NOISE. ie: Upscale Audio stringently tests and grades their tubes, per their noise, microphony, and triode balance(VERY dependable). ie: (http://www.upscaleaudio.com/tubes/12ax7/ge-12ax7.html)

Some of the NOS Mullard, Telefunken, and other tubes seem to keep on going in some gear, 10 years plus, only a couple of years in other. I'm talking high hour daily use also. Usually with the good NOS ones, as long as they test good, their sound doesn't seem to deteriorate. If you plan on staying with tubes, I would consider buying a Mutual Conductance tube tester. All of the tube amp people I know have extra tubes on hand. The quality of some of the newer ones are getting better, but I don't think they've reached what some NOS ones can do. Others say they've have it down now, for sonics and reliability.

http://www.audiocircle.com/index.php?topic=43982.0
It's not easy getting a quiet reliable tube.

Thank you kindly for the responses. In addition to Upscale Audio, which other manufacturers have a first-rate reputation for tube quality?