Regular MQTT Sensors have an expire_after
option. This option was later added to and MQTT Binary Sensor but not to other MQTT integrations like MQTT Alarm Control Panel and MQTT HVAC.
It would be handy for integrations that send status periodically to notice that the integration is dead. For example, an alarm system that is not sending status for a while is a reason for concern. With the expire_after
option this could be easily noticed.