Will it make my iPad battery last longer (talking about if it will affect my battery in a year or two from now) if I completely power it down when not using it instead of putting it to sleep? I know this will make the battery last longer now because even when it is in sleep mode it uses battery but I mean will it help a few years down the road and help preserve the battery life or does turning it on/off completely all the time affect the battery capacity negatively?