How long after the NVC approves a case, do you have to conduct your interview at the embassy, before the time expires for your CR-1 Visa?

For example, suppose the NVC forwards the case to the embassy. Then the couple encounters an unexpected problem that would cause indefinite delay (family issues, relationship problems, acute illness or hospitalization, financial distress, etc.). Meanwhile the embassy issues an interview date, but the couple needs or decides to delay the interview for an extended period of time... how long do they have before its too late?

For example, the NVC says if you don't send in the DS-230 within 1 year of it being generated, you have to resubmit all your documentation and fees to continue. Is there a different deadline AFTER the NVC approval, or would the same deadline still apply?