Apple mail threads

I see a lot of people asking about turning off conversations view in Apple Mail, but no one seems to have answered about turning it off for all your mail folders. I can do it one at a time, but I have multiple levels of nested email folders (hundreds of them), and absolutely hate conversation view.

I've tried, as suggested elsewhere, expanding all the folders, selecting them all, and then selecting view->organize by conversation -- making sure it is unchecked when done. But then when I go back to individual folders they are still threaded.

Anyone got a surefire hit for globally switching it off, and leaving it off?