How often do you swear oaths by Shai-Hulud?

The only oath i ever swear to is "i solemnly swear I'm up to no good." And that is it. End of story.

Only on fremen high holy days..
Or when a new water cache is consecrated in the subterranean vaults on Arrakis

Once every....who?

On the full moon

Even the fremen don't.

Never