Hi everyone on here. I would like to know please, why it appears as if a 2x18650, single xmlt6 torch, appears not-quite-as-bright using fully charged Sanyo’s ? - as opposed to maybe 20 min after using it ( not continually ) - it seems brighter. Seems odd to me it should be brighter with lesser-charged cells. I do not usually ‘rest’ the cells before I use them after a full charge - is that the problem?? thanks.
Placebo effect?
During 20 mins it gets darker outside, and relative brightness of flashlight is higher?
Try using meter of your camera (if you have one) as “brightness measurement tool”, but do it in area with no ambient lighting (e.g. your room with lights off during the night)
I would assume the same thing Shadowww said. If you had a lux meter, you could tell for sure then.
Could possibly be all an illusion. Mind you, each time I use the torch, it is pretty much in the same relative darkness. However it’s not an issue for me so cheers guys, I thought there may have been a ” known ” reason for what I am seeing 
There is a known reason - your brain/eyes can't be trusted.
I have some lights with programmable drivers, and if I set one mode to 100%, and another mode to 70%, it's very nearly impossible to tell the difference. The second mode has to be down at under 50% before there's an easily noticeable difference in brightness. So, there's no way your light is getting brighter by enough to notice it by eye, since that would require a jump of around 50% more light...
There are several drivers that deliver more power to the led after the batteries are somewhat depleted than when full. Some drivers for multiple batteries gove more power to the led when unsing 2 batteries than when using 3. There are quite a few eqmples of this in various flashlight reviews and driver reviews. That may be what is happening with your light.
Which light?
I honestly don't remember Werner. Sorry. Just notice it sometimes in reviews. And some of the reviews of driver where you can see it happening on the voltage sweep graphs.
EDIT: Trustfire TR-J12 is brighter on 2 cells than on three. See here