[Ringz]

I have sealed TDK MA-XG in mint condition. Stored in a dry, dark place. Do you say that they are degraded now?

[Hackbraten]

Your metal tape might be fine if stored well. Chances are you're never going to unseal it anyway.

There are, however, reports of degraded batches of the TDK SA series [0] and other brands.

[0]: https://en.wikipedia.org/wiki/Sticky-shed_syndrome