If you do not use the message function, turn it off.

Messages are automatically deleted after a set amount of time has elapsed since they were posted. Please set the time for automatic deletion before using this function.
You can also set the auto-delete time when sending a message on the message screen. It will take precedence over the auto-delete time on this screen.

[ For those on the Pro Plan ]
　Please note that your message will not be indefinite unless the other party has the latest version.