A new update is expected to arrive in WhatsApp soon to help manage the number of messages in chat broadcast or broadcast list.
The update will introduce a new "limit messages" feature, allowing users to set a monthly cap on the number of messages sent in a particular broadcast.
WhatsApp will display the number of recipients in the broadcast as well as the number of messages remaining out of the total available.
The new broadcast chat features are currently available in WhatsApp Android beta 2.25.10.8, and will be rolled out in the stable version soon.