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All-day battery life is based on 18 hours with the following use: 90 time checks, 90 notifications, 45 minutes of app use, and a 30-minute workout with music playback from Apple Watch via Bluetooth, over the course of 18 hours.
Re: how often do you charge your battery. I usually let my battery run down to the point of being depleted and then charge it overnight. A few of those nights, I'll charge it with the device powered off. Warrior_Bard likes this. let mine run down low before charging. Around 20% or so. On my iPhone 5S, I can go two days between charges and on my iPhone 6, I can go three days between charges. I am not a heavy user.