Just got my ipad 2 today! Got to my local Apple store at 5:15am and was 8th in line. Got my 32gb black and love it so far. This my seem like a really dumb question, but do i need to turn my ipad off? Or is turning the screen off (which will automatically go into sleep mode i assume) be sufficient to getting the most out of the battery? I apologize for my ignorance. First time ipad user.