I always charge to 79-80%. I had been using the included 5 watt charger, but it was designed to use with the dinky iPhone 4 battery which is half the size of the Plus size batteries, so I recently started using the iPad charger. I just don't have patience any more for that little 5 watt charger. It's a time waster. The iPad charger WILL heat up the battery a little more while charging below 80% because it dumps in a lot more current: 7+ watts. So it's not a good choice if the ambient temperature is hot - hot day. If I'm charging the phone unattended, I sometimes use the app Charge Alarm Pro https://itunes.apple.com/us/app/charge-alarm-pro/id1071191623?mt=8 especially now with the iPad charger because that charger charges much faster... The app will alert me to unplug. It will sound an alarm when the battery charge hits your set point (any percentage you choose) but it has to be kept in the foreground to work. I had an old iPhone 5 I used to use years ago (still have it in a drawer) that I used to use plugged in all the time - keeping it at 100% all the time - and the battery swelled and lifted the screen. So I don't recommend doing that ever.