If you're going to store your device for a month or more, don't leave it at zero percent. Lithium-ion batteries hate being fully discharged. They can fall below a safe voltage and won't charge properly again.

Instead, charge it to about 60% and then store it. That's the sweet spot for battery longevity. If you use it regularly, you don't need to worry about this—just don't let it sit dead for weeks.