About a hundred years.
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What have been your experiences using tubes made in the 21st century that have been sitting on a shelf for, say five to eight years?I have no experience meeting that description, but FWIW I have many tubes in my antique radio collection from as far back as 1922, manufactured when tube technology was in its infancy, which work perfectly fine. And which in most cases were probably sitting unused for many decades during the intervening 90 or so years.
how many NOS tubes have to be discarded simply because they went bad in their boxes while sitting unused.That's an easy one to answer. Based on my experience, just count the number of "NOS" tubes added to ebay each day and multiply by the number of days since ebay was first launched. That'll tell you how many NOS tubes have gone bad sitting on the shelf, because I have NEVER, EVER, EVER bought an NOS tube from an ebay seller that measured close to NOS. In fact, less than half actually measured "good" on a calibrated Hickock Tester.
I have a lightly used ARC SP3 which I bought in 1975. It still has the same tubes I bought it with, and it works fine. The preamp sat unused for about 15 years, then I sent it back to ARC for the 3C upgrade in 2003. ARC tested the tubes and said they were still good. I have been using it lightly since 2003 and it still works fine and sounds great. Original tubes!!
If one buys tubes that do not measure in the, "NEW" range,
calibrated tester, but were described as, "NOS," either the
seller didn't know what they were selling, or they lied.
I've bought almost a hundred tubes, off eBay(some from
Germany, Australia, Argentina), in the past 9 years,
searching for the most accurate sounding/best sound stage
combination of phase splitter & driver, for my Cary
monoblocks and the output stage of a BAT VK-D5. All
purchased have been 6SN7GT variants, from
the 40's(ie: TungSol round plates, Sylvania 6SN7W tall/metal
base, Ken-Rad CKR, Sylvania VT-231 bottom getter and so on)
with the exception of a few Siemens CCa grey shields, from
the early 60's, for the CDP. I've found that if one
communicates with the seller and knows what to ask; it's
easy to tell if they know what they're doing. Everything
purchased as, "NOS" tested above, "new"
and those that I kept have given me many hours of musical
enjoyment, proving reliable(long term). The CCa's have
been going strong, for over 6 years, in the CDP. I've also
got a collection of tested back up tubes, for when the ones
in use are expended(the inevitable). My output tubes are
GE 6550As, from the early 70's(purchased NOS/not on eBay).
There's nothing to
dry up, wear or leak out of a vacuum tube, that's stored on
a shelf, outside of the possible entrance of air. If it
"GOOD" and not gassy, there's no reason it can't
perform as long, or longer, than a new production tube.
Like everything else: CAVEAT EMPTOR
If one buys tubes that do not measure in the, "NEW" range, on a calibrated tester, but were described as, "NOS," either the seller didn't know what they were selling, or they lied.Exactly. Either way they were not NOS. My life is far too busy to hassle w re-packing, paying for shipping, and HOPING to get a refund. I buy tubes from dealers w established reps on A'gon or their own web presence and a long history of honesty. I'm glad you've had good luck on ebay, Rodman. I was just venting (pun intended). You are of course correct, as long as the vacuum is maintained, and there are no shorts, unused tubes don't deteriorate over time. IOW, if they are good, they will stay good, assuming that they do not get physically damaged. So if you stock up on new tubes now, and leave them in a safe place, they should be fine when you use them 2, 5, 10, or 50 years from now.
So sadly true. When I got my current phonostage, a friend gave me pairs of 5751s, Telefunken ECC83s, and Amperex Bugle Boy 12ax7s to try out in place of the RCA blackplates that came with the phonostage. I had the tubes in a small box on a shelf. I accidentally knocked the box off the shelf. Although the floor is carpeted some tubes banged against each other and cracked. As it turned out it was one of each type that was destroyed so I had no matching tubes.
In the end, I settled on Telefunken ECC 803S'. I actually found a truly NOS pair that were still in their aging boxes.