Seeing as some flights will be 7+ hours, you will have to plug in your tablet/phone. How is this going to affect battery life? Plugging in a device which is using loads of resources means it’s going to get very hot, and leaving it plugged in may damage battery life.
What you could do, is plug your device in, and occasionally plug it out to let the charger cool down. Then after it has cooled down, you can plug your device back in.
Well most modern devices have built in over-charge prevention, so it’s rare to damage your device by leaving it on charge unless you do for extreme periods.
Charging your iPhone from 90% will not harm your battery either. You simply can’t overcharge an iPhone, or any other modern electronic device, for that matter. Any device that uses a Lithium Ion or Lithium Polymer battery must incorporate a charging circuit that cuts off charging power when the battery reaches 100%
Best answer nobody knows. If you uncheck the box that limits frame rate then it’s gonna run down quicker plus your graphics settings etc all contribute