Where's the eject button to disconnect my ipod?

i just bought a brand new ipod 4G 32g. Now what i want to know is that.... i heard that you should click the "disconnect button" before disconnecting my ipod from the computer, after it finished charging. (So it will last longer) BUT... i can't find the "Disconnect button" Where is it at? is it on the Computer, the ipod? exactly where is "This so called" button?