NOS Tubes inferior?

Recently new to tubes I am looking down the road to replace the tubes in my cj ls17. I was advised to look at NOS tubes vs. ordering a new set from conrad-johnson. Another friend suggested that tubes made today employ better technology and therefore are better than NOS; furthermore he stated that since glass is not 100 percent impermeable old tubes have lost some 'vacuum'. Any thoughts on this argument? Are NOS the way to go and are they worth the cost?
If you like the sound of your CJ preamp as it is now using the stock tubes, then buying their replacement tubes will preserve that same sound.

NOS tubes should probably be tested to make sure they are still good. There is no general answer. There are some great sounding NOS tubes, and some great new tubes like the Russian made 12AX7LPS.

Anyway; the brand of NOS tubes you are most likely to hear about are going to be the good ones.

I own C-J for both my amp and preamp, and although the models I have don't use the 6922 tube found in the '17, I will tell you that in my experience, C-J picks their tubes primarily for reliability of supply and for longevity, rather than strictly for sound. I've always been able to improve, IMHO, the sound of my amps by going to brands other than the ones C-J uses, but sometimes at the expense of shortened tube life (though not always). C-J is good about pre-testing their tubes, but you pay for it. You can find other reputable tube merchants who will test a wider variety of tubes and don't charge any more, often less. As for NOS, I shy away because of the cost, and because the few I've dabbled in have exhibited noise problems. However, I may not have gone far enough, both financially and in terms of seeking out a specialist dealer, to serve as an advisor here. There is little doubt that it is possible with many tube types that the best ever made are now NOS, and it's generally acknowledged that manufacturing quality was often superior during the tube's golden age, but finding a to-spec set of these without getting burned can be another matter, and the degree of sonic improvement is open to debate and will vary with the tube type in question. For the sound I've been able to achieve and am happy with, it's been simpler for me to just audition all of the currently manufactured brands and pick my favorite. At least you can count on fairly consistent results that way, and save some $ in the process. Just my $.02, I'm sure many others will come along and post about what you'll be missing if you don't investigate NOS, and probably give you specific recommendations - and they could be absolutely right, but ultimately, you'll have to decide for yourself whether or not to take the plunge. Good luck!
6922? Bad luck!
The dutch made Bugle Boys thrash all current production soundly, even given that yes, glass is porus to (mostly) low molecular weight gasses such as hydrogen and helium - fortunately present in low concentrations.

What will realy stuff tubes is being stored in damp conditions, a little water vapour will reck a tube in a few hundred hours of running.
If you go this way buy tested tubes from a buyer with good and extensive feedback.
They will cost you several arms and legs - which I would spend otherwise on upgrades, unless I had LOTS of money, which I sure don't (even though I still spend heaps on hi-fi!).
Just make sure you enjoy the music!
Sugarbrie's advice in his first sentence is right on the money. I have found that well-tested NOS tubes sound vastly superior, and have had a far longer life, in my Jadis equipment, but keep in mind that the stuff I have was made in the late 80s and designed way before that around the then-available Telefunken and MO Valve tubes. A modern piece of electronic equipment is often designed around what's available today, and may well sound excellent with current tubes.

I disagree with the premise, though, that today's tubes are better--I've had too many experiences with new tubes that are supposedly better technology (NOT materials, mind you--that claim cannot be made, in my view) and measure superbly that sounded mediocre and went bad on me in less than 6 months. You have to be careful buying NOS, both in terms of their measurements and their sonic character in your equipment, but at least in my experience they have been worth their cost, both from a sonic and reliability perspective.
If you love the sound of your CJ, stick with the same tubes. CJ isn't cheap but, they are consistent. Many new and NOS tubes are great but will definitely change the sound. Using substitute (7308) will change the sound also.
Good Luck
There is a good chance that you will be dissapointed with NOS tubes if you try only one brand. There is no reliable predictor of how a specific NOS tube is going to sound in your system without trying them out. Hence the term "tube rolling" which is the act of substituting several brands of a tube type in your equipment to find the best sound. This can become very costly depending on the number of brands you try and how exotic or scarce the tube brand is. For example, you could spend upwards of $200 on a matched pair of NOS Amperex 7308 gold pins and there is no surety they will sound good in your system. You can increase your knowledge on the NOS subject by visiting the Vacuum Tube Valley website. They have devoted magazine articles to the 6922 tube and its close relatives such as the 7308 where they test as many as 50 different tube brands and vintages for sound quality, noise, and gain. The good thing is that they include recent vintage tubes in the articles such as the sovteks, the JJ's and the EI's. Again, this is a guide that will get you started but it is likely that the tubes they rate highly will sound somewhat different in your system. That has been my experience. In my opinion, tube rolling should be viewed as a seperate avocation within the audiophile world. You must be patient and expect to get some tubes that go bad shortly after installation no matter how well they measure. If this sounds fun to you, then go for it. Just don't expect to get the right NOS tube the first time around.
Well, I would like to thank all of you for the time taken to address this topic. It has been helpful and insightful. I do believe that this hobby has a real potential for crossing the 'fun' line. It can be thrilling to experiment with components and increase one's awareness regarding the miracle of music. For me, I also need to be aware of that 'line' lurking (and I have yet to know where it is, though I'm better at knowing when I've crossed it) when it isn't fun anymore.

I do appreciate this website for the opportunities to discuss what we are passionate about. Thanks again for all of the input.