If you turn off the WiFi feature, the battery last much longer, plus it quits asking you if you want to connect every time you walk by a coffee shop.

If you need to absolutely maximize battery life, you can:
- turn off WiFi
- turn off Bluetooth
- turn off Location Services (i.e. GPS)
- turn down screen brightness
- turn off push
- and in extremis even turn off 3G (i.e. use 2G)
All this is easily turned back on when you want it. If you do all this, the battery life is a lot longer.
As a practical matter, I just turn off Bluetooth (have no BT accessories) and occasionally turn off WiFi.