Low battery indications are set to display when the lock box has about 10% of battery left. There is wiggle room to allow time to change the battery. As a reminder, low battery email notifications need to be set up on a per lock basis from the website; in-app notifications and lock light color changes are automatically set to display.
Battery power is only used when the device is awake, so the battery longevity is tied to use. Extreme weather can also have an impact on batteries, but this should not impact any of the lock boxes from MIBOR's conversion event.