Although I haven't done a lot of testing, I believe it should run for over a year on a pair of AA alkaline cells. This will be affected by the power requirements of additional sensors, supply voltage (either 3.3V or 5V can be selected) and data transmission frequency. The basic board with no additional sensors draws less than 5µA while sleeping.
The AA XBee Node includes an accurate real-time clock (DS3231, ±2ppm from 0°C to +40°C) for precise timing of data transmissions and an accurate on-board I2C temperature sensor (MCP9808, ±0.25°C typical). A prototyping area is provided for connecting additional sensors. Twelve microcontroller GPIO pins are available to interface with sensors, including the I2C and SPI buses and analog inputs. A pushbutton switch and an LED are available for application use if needed.
For more informationThe Double-A XBee Sensor Node is an open-source project. For complete information on the circuit design, including Eagle files, configuration options, programming requirements, etc. see the GitHub repository.
For an example sketch, see the aaXBee sketch which is part of my GroveStreams library. Using this sketch, the AA XBee Node sends data to an Arduino running the gsGateway sketch, which forwards it to the GroveStreams web site.