There are certain things which mobile phone users do which gradually decreases the run-time of their battery resulting in frequent battery drains and self-discharge. Smartphone batteries have a lifespan of around 2-3 years. There are ways to keep the smartphone battery healthy.
Charging smartphones all the way to 100 percent shortens the battery lifespan. For optimally utilizing the battery, charge it to 80 percent and always maintain the battery level around 55 percent. If the battery level goes down below 40 percent, charge your device again for maintaining the optimal battery level.