[whpalmer4]

Make a dummy project, perhaps by duplicating your biggest project to date. Paste in a lengthy bunch of text as a note, as long as you think might reasonably happen. Select the project, copy it, paste it a few times, select the bunch of dummy projects, copy, paste a few more times, repeating the process until you have about as many of these projects with lengthy notes as you think you might reasonably expect. See if OmniFocus behaves appreciably worse. Delete the dummy projects and make your decision on how to proceed.

I don't think you have to worry about OmniFocus being any more prone to losing or corrupting notes than any other part of the database.