Mean Time Between Failure (MTBF)

This is really handy and would like to implement it in my model, however my data model is structured abit differently. I have a fact table (Notificatons) with notification data (notification, location id, breakdown status) and this is connected to a dimension table  via "notificaiton" field showing the start and end times of the notifcation (lets call it MTBF table).

The fact table is connected to another dim table (location data) via location id and this contains the machine field. I am not sure how to determine the next_repair with this current model, any help will be much appreciated