I have almost 25 year Sony EF Sealed Blank Tapes. It still works beautifully, no shedding, squeaking etc. And I live in a very humid place. These tapes were kept simply in their box.
Interesting fact is that I also had a couple of boxes of TDK D tapes kept along with the Sony's. While these too do not have any fungus, shedding, squeaking etc, a couple of them had severe drop-out problems at either ends of the tapes.
Another interesting fact is that the TDK tape seems thinner than the Sony. No, I have not measured the thickness, it just feels like it.