The authors of the WABetaInfo portal traditionally analyze beta versions of WhatsApp for Android. Now they found an innovation there,
Now when you turn on the DisappearingMessages, you can set messages to disappear after 24 hours, 7 days, or 90 days after being sent. You can also enable disappearing messages by default for all new individual chats.
WhatsApp beta now has a new checkbox in the message timer settings:
As you can see in this screenshot,Finally, the messenger will allow you to set a message timer for several chats at the same time. The feature will help users quickly convert some chats to those that support disappearing messages. If you set a message timer for some chats using this feature, all new messages in them will disappear.
When the option will appear in the stable version of the application is not yet clear.