If you would like to lengthen your iPhone battery life and lifespan, here are the general tips from Apple:
 

  1. Always update your Apple software to the latest version. Latest iOS 9.3.1 include advanced energy saving technology. When your battery charge drops below 20%, iPhone will prompt the user to switch to battery saving mode.
  2. Avoid extreme ambient temperatures. Device performs the best in temperature range from 16° to 22°C). Exposing your phone on temperate above 35°C will damage your battery capacity. Also, charging the device in high temperature can further damage it. Using the device under a very cold environment will get a obvious decrease in battery life.
  3. If you plan to store your device for longer than 6 months, charge it to 50% every 6 months
  4. Adjust your screen brightness or dim the screen to extend the battery life.
  5. Use Wi-Fi whenever possible since it consumes less power than a cellular network.
  6. To improve your iPhone battery life, monitor your background activity and increase the fetch interval if your Mail or Calendar app is running in the background.
  7. Turn off location services in Settings > Privacy > Location Services in order to save iPhone battery life
  8. Turn off push notification in order to minimise the phone display being wake up when lock screen is displayed
  9. Turn on the aeroplane mode when you are under a poor cell coverage