It sounds like you are concerned about the Standby Time increasing using your battery excessively. Here is some info about what the Standby Time indicates and why it keeps counting up when the device is asleep from the article named:
iOS: About standby and usage time
View Standby to see the amount of time the device has been turned on since its last full charge, including the time the device has been asleep.
Here is another webpage that you can use to help optimize your settings to extend your battery life:
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