Some one needs to invent app that shouts smart phone off after 15 minutes of no activity just like on windows computers.
If an app existed it would mean that you would likely miss phone calls because phone would be off when someone is calling. Additionally each time you wanted to use the phone you would have to boot it completely up.
I have a LG16C smartphone from 2015 and to extend my battery life I shut off the 3G internet connection. This way it can still be used as a phone. When I want to get online I enable the data connection to 3G do what i need to do and then shut off the data connection.
Phones will run dead faster when data connection is enabled and also far from a tower or inside a building where it needs to increase its signal to overcome loss to try to maintain handshake with tower.
If I leave my 3G data connection active and go into my work where there is no cell or 3G signal by smart phone will go maximum output to try to establish connection and battery completely dead in about 4 hours. With me shutting off the 3G data connection I can go almost 30 hours before battery dead.
