Thanks for your ver informative reply Edit. Omg (haha), <-- that smiley almost makes me reconsider anything Japanese!! I dare not do the tongue-smiley! I understand that all rechargable batteries will die after so many charge cycles, and also that li-ions can deteroiate in other ways; or through other means rather, than simply charging and draining. It's also good news to hear that it is potentially possible to find a replacement 'internal' battery, once one starts fading. (80% after 1 year at typical usage? Would that be 60% after 2 years? 50?) I don't entirely understand this: " Where the "internal" batteries in these units can easily be purchased from Sony, the cost of the "internal" ones are usually high. However if it is using a Li-Ion-Polymer battery (or even a standard Li-Ion which connects internally with wires instead of contact points), " Does this mean that some internal li-ions that sit in Sony players are connected via contact points? Anyway, are the E4/5/A6 series of flash players equipped with batteries that would be potentially exchangable(pure li-ion or li-ion-polymer with wire connectors), do you know?