So if I have an audio file that plays for 1 min, 10 mins or 60 mins, I want this text information to be continuously displayed, at all times, UNTIL the text file changes.
Yes, the text disappears because the file has changed and is now probably empty. This is the basic function and it must be so, otherwise the track would continue to show even though it has long since finished playing. There's no secret way how the software recognizes if the track is still playing or not. The text file provides this information, assuming: track name is present = the track is playing, no track name = no track is playing.
Our task could be: how to preserve the last text in case it is no longer available. The Magic RDS 4 provides several methods how to implement your requirement. The simplest is to fill %GOTONEXT% into the N/A text field in the Text Source editor. This will prevent sending empty text. If there's no other source in the loop, the track will stay on the display.