[Leica] How long is an M8 battery supposed to last ?

[benedenia at gmail.com (Marty Deveney)]

I have three Leica batteries and five of the eBay third party ones.
My original Leica one now only shows two bars on the camera when I
fully charge it and put it in, but I seem to get about the same number
of shots.  It's been through a charge/discharge cycle maybe 30-40
times.  I I have no idea how many cycles it might be from needing to
be discarded; maybe they fail catastrophically, or maybe they just
eventually run out of steam.  I'm interested to know if anyone has had
that happen, apart from ones that arrived dead in the box (one of my
Leica ones came that way and was replaced, and I have read that some
of the third party ones have shown the same problem).

Marty