Single Use Key Pairs: Disposable Private Keys?

If an NFT (for a photo, a calf, or a kiss, etc.) or a unique one-of-a-kind business document (a specific purchase order, invoice, waybill, delivery confirmation, etc.) is represented as a (signed) verifiable credential, once the proof is generated for the VC, is it necessary to persist the private key used to sign the VC?
...can't the private key be thrown away if it is no longer needed to sign anything further?
...that is, only the public key needs to be persisted and keyed to the VC's outer id and stored in the corresponding DID document?
... inspired by the early part of Sam's KERI ssimeetup talk.

Michael Herman
Founder
Trusted Digital Web
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