in addition to this great post I'd like to point out that you'd have to define your "minimal usable light" from the light, and measure the area under the curve (AUC) according to this criterium, the longer glimmer of the unregulated light should not count here, it will be useless for you.
another point to consider is that regulated lights don't give you a warning that the batteries are about to fail (unless they have a battery indicator as the ElteMax does), whereas the unregulated torch is steadily dimming.
bernhard
EDIT: just to add my personal view ... I am all regulated !!!
I like a tool that always performs in the same manner no matter how drained the batts are. with the very reliable regulators we have now I do not see a problem on the technical side. the only thing I really miss are battery status indicators, IMHO this is a must-have feature in the future of regulation. that's why I really like my MR-X ...
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