Battery life of the E71 phone is exceptional when compared to other Nokia and other brand phones. I think Nokia has taken a big leap with this.
However, one always likes to get the best from the battery. Nokia tips has a good post on how to 
increase the battery life of a smartphone which applies to E71 (because it is the smartest 😉 ). What is good about the post is that not only does he give suggestions on what to do but also how to make the changes which are illustrated with help of pictures.
Briefly Mobile Jorge (post writer) suggests the following
- Set your screen brightness to Minimum
- Turn off Bluetooth
- Make sure WiFi scanning is off
- Set your power saver timeout to its least value
- Set your light timeout to its least value
- Set your phone’s profile to "Offline" when you dont need to make/receive calls
- Lay off the gaming, music or data transfers
- Lay off the GPS
- Make sure there are no background Applications running
- Lock your Keypad
For details and how to implement each task you can go to the post at http://www.nokia-tips.com/2009/08/18/10-tips-to-stretch-your-battery-life-2/.
Source: Nokia Tips – 10 Tips to stretch your battery life on your Nokia Smartphone
