it makes sense that the batteries don't last long. Since we haven't discussed the power management part of the code, you're in active mode the whole time. The power drain will be high and you won't get more than a day or two of battery life.
What you need is to disable any peripherals you're using and put the Wildlogger into powerdown (aka sleep) mode. Then use the real time clock to wake your system up periodically to take measurements, say every hour. That's actually going to be what we do in module 5 which I'm actually working on right before I took a break to check the interwebz.
With the right power management, you should be able to keep the system going for a month or longer depending on the power draw of the sensors you want to use. With the DHT11, PIR, and SD card, we estimate around 2.5 months but that depends on the power draw of the SD card.
If you can have some patience,we'll be working on and finishing out module 5 soon. We'll let you know when it's available. In the meantime, if you need to deploy soon, I recommend you check out the Low Power library for Arduino and look at the examples.
Hope that helps.