Leaving your iphone screen on while plugged in

Not sure if it'll hurt the screen but I think it may reduce the life span of your Li-ion batteries due to higher temperatures that the device may generate..although I am not sure how warm the device will get with the screen on for a long period of time. I hear that notebooks that run hot are a victim to these issues, and it is recommended to remove the batteries when using plugged in for a long time. Obviously this isn't an option for you.