Yes, Classification Rule Builder has a maximum 6-month lookback window.
If you want the values to look back forever, then you should use the
Classification Importer.You could probably test your proposed RegExs by
downloading the existing campaign tracking codes (from Classification
Importer) to test your RegExs with.If you're worried about overwriting
unexpectedly, you can do this:Test your RegExs like what I had
described.Update your Classification Rule Builder with a 1-month