I've just found this app Accubattery. If you charge your phone to 100% every time it takes almost 1% out of it's life. Only charge it to 80% and you only take 0.2% out of it's life. I've no affiliation with this app just give it a try and I'd like to here your comments.
Martyn
Never thought about that trick but according to me is about how old mobile phone your using. Because after 3 year old mobile phone battery start to decline.
Don't trust these apps.They are there to promote themselves.
https://www.wired.co.uk/article/how-to-improve-battery-life-tips-myths-smartphones
https://www.androidauthority.com/battery-myths-688089/