Sanyo ENELOOP seem to be the choice for long lasting battery power. They appear to hold their charge up to 75% for one year. A video of the older 2000mah is only here:
You can now buy the 2500 version off Amazon. I’ll definitely will buy a pack of those for the soon coming SB900. For all of you who were looking for some batteries check this one out. I found it very helpful and you’ll find this useful too.