Hi Alien Nation,
Thank you for the compliment, it is appreciated.
The NIMH batteries retain the charge quite well and have a self discharge rate of 1 % per day.
Even the best Sanyo batteries self discharge at this rate, I am always in the look out for a better battery for my lights, and I have changed a few months ago to the new POWEREX 2700 mah that have high current capabilities and has been proved to self discharge at 1/2 of 1 % per day.
Anyway I recommend my customers that they do top off the charge every month (I do it every time I pay my phone bill and rotate my magazines), it just take only a few minutes in the RC FAST charger (90 minutes for a full recharge).
An important part of the equation is how you treat your batteries at the start, when I built the lights, I give the new batteries two forming charges (a base for subsequent charges) in the slow Vanson charger (12 hours each time)
I then match them for the exact capacity in the La Crosse 900, that way with matched capacity they finish the charge all together and the customer get maximum brightness to the very end of the run time, (50 minutes).
There is in the market a new class of NIMH batteries pioneered by Sanyo, Eneelop in the Sanyo brand, they retain the charge even much longer and can stay charged for a full year, the only thing is that they have a reduced capacity of 2,000 mah giving the BOREALIS only 35 minutes or so.
The Eneelop are high capacity enough to cope well with the 3150 mah demands from the BOREALIS' bulb.
Now RayOvac is coming out with its own version and Titanium has another in the market, but I haven't tried these two new brands in the Borealis, so I can't comment.
I do have provided the Eneelop to some civilian customers that wish to store the flashlight and forget it for a long time.
I use Nimh rechargeable for everything, cameras, GPS, Laser range finder and two way radios are some of the gadgets that drink battery juice like no tomorrow, the rechargeable Nimhs give me guilt free usage of these gadgets and I will never pollute another landfill or throw money away with alkaline.