Lithium-Polymer battery charging question

Factual Questions
1

I bought an extra Lithium-Polymer battery for my one-year-old Kindle from BatteryShip. When it came I put it in the device and gave it a full charge. Then used it until it got down to one bar, recharged fully, and took it out and put the original battery back. I put the new one in a ziplock bag and in a drawer. I know these don’t have a “memory” problem so don’t have to be fully discharged at first.

OK, finally, the questions:

  1. How long will the charge hold in this spare battery, not being used or connected?

  2. Would it be prudent to put it back in and recharge periodically?

  3. If so, how often?

OR

  1. If I just leave it alone, will it eventually lose all its charge, and if so, will it be harmful just to leave it alone until needed, and then give it a full charge?