On Sat, 08 Sep 2012 11:06:05 +0100, AJH
wrote:

e.g. if the battery is maintained charged and not
used (only self discharge being an issue) how long a life?

Around four years seems to be what you can expect under those
circumstances. There are improvements going on all the time with
lithium chemistry, but shelf life seems to be fairly static.
Iow, if I'm offered a brand new battery pack that's four years old and
never been used, I'd want it for nothing so I can see if it's any
good. There's no way I'd pay anything for it until I can see exactly
how it's fared in storage.

I've been messing around for the past couple of years with leccy bikes
and garnered some knowledge of battery packs, but the people who could
really answer your question are on www.endless-sphere.com