What are the Success rates of K1 Visa Couples getting Approved if there is a significant age difference?

The truth is, Couples who have large age differences may face more scrutiny than closer to same age couples? Although Interviewers for many years have been used to seeing wide age differences and accept it, provided the K1 Fiancee applicant can demonstrate that the couple has enough supporting documentation to prove the relationship is genuine and sincere? The only way a couple can do this is with time spent in emailing, sending postal letters, calling on a regular phone and sending each other gifts.