One can set time to 24 hours, 7 days, or 90 days for disappearing chats.
Once the user turns on thedisappearing messages feature, their chats will be deleted after 7 days.
Last year in November, the feature was launched and had the option of disappearing messages after seven days.

According to the company, turning on disappearing messages by default will not affect the existing chats.
When you turn on this feature for all one-on-one chats, your existing chats will not be affected.
Whatsapp warns the users that the disappearing messages feature should be used with trusted contacts only.

As we dont know what happens in future.
How to Turn On Disappearing Messages Feature on Whatsapp?
you’ve got the option to set the time limit as per your choice from the given options.

If you want to disable, then follow the same steps and pick the off option.
