What should you change to increase battery life:
1- The easier way to gain battery life is to reduce brightness. I had my SP3 at 60% and getting around 6.5 hours of battery. Reducing the brightness from around 35% to 40% increased battery life to around 8 hours.
2- The next recommendation would be to adjust display off time in the Balance Power Plan, I'm using 3 minutes
3- Leave in the Indexing options only the folders where you have your libraries: Music, Videos and Documents. Remove "Download" and other folders like Windows, Program Files, etc.
4- Remove from Start up all tasks and services that you don't need like Google update, google crash manager, etc. CCleaner
is a tool that can help you in this task.
5- Do not keep Apps opened if you don't need them. Close what ever you are not using, do not leave it opened in the background.
6- Turn off all the notifications that are not really needed.
7- You can turn off Bluetooth adapter to gain few more minutes in an emergency
8- Microsoft recommends at least once a month to leave the battery drain up to 10%.