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Certainly the cell pack of a Kindle Keyboard has 3 wires and a built in controller.
However most gadgets that have a "naked" cell do have a controller on the main PCB.
You can't trickle charge a Lithium cell at all when it's fully charged or it can go on fire, unlike NiCd and NiMH. The NiMH life is short if the trickle charge isn't very much lower than used to be common for NiCd, so not all older gear with NiMH replacing NiCd can be left on charge when charged.
All chargers for gadgets are dumb, only sense if any is on USB data lines. Only chargers for naked cells are smart.
All gadgets with Lithium cell(s) and USB for charge or a separate charge socket must internally implement disconnecting the cell if voltage is too low and stopping charge when it's full. Only some implement cycle tracking and capacity tracking using either a CPU in the cell pack or in the gadget. It's just some may not implement it well.
About 2/3rds charge is best for long storage. Unfortunately the Kindle doesn't turn off until the cell is discharged! So an unused Sony, Nook or Kobo will have longer life than a kindle. The life should be the same if occasionally used.
So an unused Kindle should be checked and charged if below 1/3 or 1/4 and if being stored, stop at 2/3 to 3/4.
Store in a cool dry place maybe above 4 °C.
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