Temporary failures are supposed to be temporary. Some addresses soft-bounce on every campaign for months.

A mailbox that has been "full" since spring is effectively abandoned. Retry logic keeps knocking on that door, and the provider keeps counting the failures against you.

A reasonable rule is to suppress an address after several consecutive soft bounces across separate sends. The exact number is your call. uChecker's soft bounce glossary page covers the 4xx codes behind these failures and when removal makes more sense than another retry.