First you should know about two term. "Battery Life" is the amount of time that your device works without recharging. "Battery Lifespan" the amount of time that you should change the battery physically. Apple offers some tips for maximizing these two parameters that are listed as bellow and you can get more details at https://www.apple.com/batteries/maximizing-performance/
- Update to the last software
- Avoid extreme ambient temperatures.
- Remove certain cases during charging.
- Store it half-charged when you store it long term.
- Optimize your settings.
- Enable Low Power Mode.
- View Battery Usage information
- Plug in and power on your computer to charge your device.
