How long will the battery life on a battery powered Metron4?

This depends on the regime, i.e. how often readings are being taken, how much power the sensors need and for how long, and how often readings are being transmitted. There are external factors which will effect battery life such as temperature and the local network conditions but in general if we are taking a reading once per day and sending it then we get around 4 years from Metron4, though the record is an equivalent of 13 years!