[oXygen-user] Maintaining line length

In the Oxygen editor, I have set my line length in Preferences->Editor->Text-> print margin to 200. I have to turn on "show print margin" to set it to the length I require: 200 characters. Then I turn off "show print margin" and the 200 remains while I am editing. However, oxygen keeps resetting that length to "80" at what appear to be random times. What I want is for Oxygen to always allow 200 characters before wrapping the text, even when I open a file with "format when opening". Acttually, I don't want any line wrapping at all, if possible. Can you help? Thanks, Mark