Great initial post Phillip. I had recently discovered a flat set of batteries in my SB800 when I've gone to use it too. In my case it was only after 8 days and I expected a little more retained capacity.
I keep very a detailed recharging log to keep track of the 4-5 sets of
AA batteries I have. I have found that my Energizers (1850mAh) seem to lose less of their charge than the two sets of Sanyo 2500's I have. To make matters worse, the latter were manufactured a few years later than the former - I would have expect the older cells to be closer to their end of life...
I've also tried out the ReZap charger, when they were on special at Kmart's 15% off sale. I did not have success with them. IMHO they're slow to charge NiMH, which I've read from sources are not ideal for this chemistry, and when I attempted to recharge a standard leading brand alkaline battery, only partially discharged as instructed, some of the cells warped and burst. Not to detract from their marketting statement, my dad, who has made a living in electronics throughout his life, agreed that their claims of recharging primary cell batteries were not completely obsurd. Normal alkalines can be recharged (under EXTREMELY low current loads) for a few cycles, maybe 3-5 times, fairly safely. However, counter to this - there must be some merit in the warning labels placed on just about every primary cell battery that warns against recharging...