Refset Descriptor Inactivation

I'm just revising our validations for the Refset Descriptor Refset. (Upon realising after realising we had none!).

And have wondering if the entries should remain active for retired reference sets?

The specs (5.2.4.1 Reference Set Descriptor) seem to be silent on the issue... (Unless noted elsewhere)? So I've looked for guidance in the data...

The non-human refset is the only refset that I can think of that's been inactive. And it's descriptor history is a bit murky..

There's two entries, it is (was) a simple type Reference Set. I'm not sure if the 2017 entry is just noise, or incorrect somehow.

I don't mind what the answer is. I just want to write an appropriate validation rule.