Documents are obviously very valuable as evidence; however, it is surprising how often a document can be ambiguous. People may use different addresses for different purposes. There may be another explanation for the document's existence than the one that you think is obvious. Relationships can be volatile and people will not always promptly change their address.
The reported cases about whether a de facto relationship existed and when it commenced and when it ended have generally been costly to run and often last several days with lengthy and numerous affidavits and exhibits. This article establishes a list of evidence that may be of use when attempting to prove the existence of a de facto relationship.