[whpalmer4]

The backups that OmniOutliner is doing are only of your unsaved documents. So, if you set it to make a backup every 5 minutes, and at 8 AM you open a document and make some changes, at 8:05 AM, if you have not saved the document, OmniOutliner will squirrel away a copy of the document as it currently is in your open window, so that if something untoward happens at 8:06 AM (your computer crashes, for example), you can recover those changes. OmniOutliner will notice that there is a more recent backup file when you open the document again and ask if you want to recover those changes. You'll see the backup copy of the file as <filename> (Autosaved).oo3 in the directory where the document lives. When you save your changes, the autosave file is removed.

So, yes, OmniOutliner is not making long-term backups of your documents, only temporary backups of your unsaved changes, and you still need to use Time Machine, SuperDuper!, CrashPlan, or whatever backup solution works best for you to keep backups of your documents.