[Quoth]

Modern chargers in a gadget actually stop charging entirely or the LiPoly would go on fire. The controllers also typically disconnect if the cell is too low. If the cell get completely discharged it may never recharge, but that doesn't usually make it swell.
They can swell simply with age, number of cycles or temperature.

Kindles have no off setting, only a screen blank, so most iOS, Android and non-Kindles will hold a charge for months longer when unused and off/shutdown.