According to my battery monitor, I have 3 days of battery. It only gets minor use in the morning (check the news, email) and then is normal standby. I disable GPS unless I need it, but other than that I have WiFi, bluetooth, 4G all enabled. If you don't use your phone, it has a long standby time. My usage picks up during the day, so I need to recharge in the evening. I still only get to about 40% with heavy use in the evening - it is still a new toy and gets a lot of attention when I get home. If you use it, the battery will run down (I hear a chorus of DUH!). If you are trying to maximise standby time, turn off Bluetooth, GPS and internet (wifi and 4g), and switch to 2G/3G connection (depending on what is available where you are). Stop any running apps. This will mean you can still make/receive phone calls and still have multiday battery.
I am guessing you still want your phone functional, otherwise you would just turn it off - many months per battery then Things that use a lot of power are:
GPS
Radio Transmitter (eg. internet, making calls)
Screen
Heavy CPU/GPU use - eg. games
Bluetooth uses a bit - if you don't need it turn it off
Band switching in a poor signal area (eg from 4G to 3G and back). That is why selecting 2G or 3G only helps. It doesn't switch.
Turning your phone off overnight also saves a bit - the alarm will turn it back on.
I have eked out 5 days doing this with a BB passport whilst camping. Hope this helps