How long does account migration take to propagate across the Fediverse?

How long does the domain the account was migrated from need to remain active to prevent annoying other servers?

Hypothetically, if 1.domain.tld was running fedi server A and 2.domain.tld was running fedi server A, could 1.domain.tld be taken offline 30 days or so after all (one) users had migrated over? What if someone then set up fedi server B on 1.domain.tld 30 days or so after that? Would that still make the server log gods angry about the changed keys and different locations of resources?

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