what do you recommendate to extend battery life...I am not talking about the IOS, apps, screen, light..etc.. I usually let battery run out to 10% (its whole day using) and then let it charge over the night while i sleep and unplug it when i wake up .. ? good or bad? what about partial charging, like charge from 30% to 45% or 40% to 60%? is that bad ? all charging over 80%? ok or bad? I dont remember where i read that the best for battery is to charge it between 40% and pull charger out at 80% ..?