I wrote Design Pattern: Separation of Behaviors to cover just this situation. It uses alerting as the example but can be used to centralize lots of things. It is basically a more detailed description of what Udo describes.
This approach is also handy to add some logic around alerts. For example, after dark only send alerts to one of the devices. During the day use a different service than at night. Send them using yet a different service if no one is home. Stuff like that.
And this does not preclude the use of MQTTWarn which is also a great service.
EDIT: somehow the link didn’t work to the DP.