Zenseio devices use industrial-grade lithium batteries that have large energy capacity, last long time, and can function in a wide ambient temperature range. However, the battery life is heavily dependent on the radio signal strength (especially for CSMP), the ambient temperatures, and the types of external sensors attached. Here are a few tips that can help to extend the battery life:

• If the signal is weak (below 16 for CSMP), we recommend to boost it up with extending the antenna higher up (ideally above the canopy). Please see this app note: Recommendations for Boosting Antenna Signal​
• Install the devices out of direct sun exposure (position it in the shade or add cover during the noon and afternoon when the sun is the strongest). When the ambient temperatures are high and there is a direct sun exposure, the battery temperature inside the box can get extremely hot (like in a locked car). Prolonged extreme heat exposure will dramatically reduce the battery life. 
• In very low ambient temperatures, the battery will show lower voltage which will recover with higher temperatures. This is a normal behavior for this type of battery. You may still get quite more lifetime out of the batteries if you wait with replacement till spring, as long as the battery voltage is higher than 3.3V in 30's or low 40's Fahrenheit and works consistently. (But, replace otherwise, if the voltage is consistently below 3.3V, especially at higher temperatures.) 
• Turn off the sensor interfaces that are not being used. For example, if there are no sensors connected to GPI inputs, set the mode to "off" for those. Or conversely, if there is no probe connected to SDI-12 interface, turn off SDI-12.