Best way to store an ipod classic

I tend to use my ipod then store it for a week or two (or longer), depending on my schedule. What is the best way to store the ipod when it is not in use.
Plugged in through the USB port so it is continuously/fully charged at all times?

Unplugged and off (the battery slowly drains)?

Any danger if not used for extended periods of time? ie battery totally drains