@Alex SE : well, we just talked extensively about keeping tapes wrapped or using them.
I am not a collector then, sooner or later, I will unwrap and use all the NOS sealed ones I have here, regardless of their rarity or age.
At max, I would understand keeping only one wrapped example of each model and using all the others so, about that SA-X from 1982 of yours, you have two of them, then you can use one and keep the other one sealed.
Btw, I just unsealed and tried a few very rare tapes which I had only one example of each... watching at them sealed and never knowing how they do sound is something I would surely regret... so I opened a few of the ones I own only one example by I tried to cut the shrinkwrap carefully and keep it stored between the pages of a book.
@J!m : I perfectly remember all the debates about the reliability issues regarding so many TDK cassettes there in the other place.
Of course, I cannot doubt about other people's good experiences but, at the same time, I cannot ignore the incredibly high failure rate I experienced myself.
So, it might be a matter of luck?
To me, the failure rate of TDK tapes made from, say, 1988 to the end (early 2000's ?) is extremely high and not comparable to any other brands.
And this is, sadly, a matter of fact here, not an impression or speculation.
For example, I've bought like 40 sealed TDK MA from 1990-91 vintage, all with made in Germany written on, and got them from two different sellers at two different zones of Italy and all of those tapes, none excluded, are affected by the white powder issue.... so, 100% failure rate here on those.
But I experienced also other kinds of problems with certain TDK tapes here, I believe I've experienced any possible kind of problems and, usually, the failure rate is at least 50% if not even more.
What can I say? Maybe I am the most unlucky guy on earth about TDK... but that's it.
Resuming, the TDK models/years I had problems with (and not one single tape but most of them) are:
TDK MA from 1990-91 (gold-black wrapper) = white powder issue
TDK SA from 1990-91 (gold-black wrapper) = greasy transparent lubrificant issue
TDK SA from 1992-94 (blue wrapper) = super fragile tape on thin tape (c80, c90, c100 lenghts) , then railroads as soon as you try to use them
(*)
TDK CDing2 (later versions, from late 90's to early 00's ? ) = greasy lubrificant, to the point of getting a huge amount of modulation noise
TDK DJ2 (late 90's to early 00's ? ) = greasy lubrificant, same as the CDing2... some tapes literally cause W&F and the deck into stop mode
TDK D (mid 90's) = fragile tape, it railroads after first use even if the tape lenght is c46 and then the tape should be relatively thick
(*)
I do also remember that, there in the other place, to let people realize I was not being a "TDK hater" as they maybe thought but I was simply describing my own experiences, I had freely donated/sent a bunch of such problem TDK tapes (still sealed ones) to a guy abroad to try them and see... and he's got the same bad experiences as here.
So, if anything, I'd say it's impossible to make a general rule that they tend to be all bad or all good... some were lucky and got a negligible failure rate, some others (i.e. myself) got an incredibly high failure rate, up to 100% on certain models.
Btw, I would be happy to know if there is a way to fix the white powder issue of the TDK MA i have here, so that I would not be forced to stop the deck and clean the heads/transport each 5 minutes of tape running... these tapes, if i do ignore the point that they release that white crap on the deck, would sound great and would measure awesome... in fact, they are some of those metal tapes which give me a nicely high measured MOL also on those decks which struggle to get a good MOL on other brand's metal tapes.
(*) : member "meabster" at the other place finally discovered that the railroading issues might be related to badly made guide rollers which don't show a plain/smooth surface (they have a sort of ridge) and, also, some of those rollers, on a random base, happen to be mounted the opposite way as they should, not being exactly symmetrical and then with a preferred way to be fit into the shell.
Anyways, on certain TDK shells like the clear ones used (i.e.) for the later versions CDing2, I've noticed the guide rollers are eccentric or not rounded, in fact, they turn wobbly... it's easy to see on those clear shells, you just need to give those guide rollers a watch while they are turning.