Ah, now I get what you were trying to say. Lumen output per watt of power input. Yes I can understand that you can only go so far in that department. As to the Pelican yes it does its job but the new version puts out twice the Lumen and can use not only NiMH and Alkaline AA size cells but also Lithium 3.7V and LiFePO4 3.2V cells in the 14500 & 14505 size as well. Its got a brighter emitter with a control circuit that can handle a wider voltage range. Technology improves over time and the new stuff (provided it is still made with the same level of quality) becomes better then the old stuff.

My main concern is not to over-pay for an item that is going to become outdated in two to three years or so but at the same time pay just enough to get decent quality that will last at least three or four years (about a year longer then the expected replacement time period) under daily use and then upgrade every two to three years or so and retire the old one to backup/spare status rather then daily use at that time (my current Pelican is just about to be so replaced with the new model). Either that or do your own full custom build if you want something that is "made like they used to make them". The prometheus flashlights under discussion in this thread violate that rule considerably too rich for something that is only semi-custom and as I said in only a couple of years will be outdated. Defining "outdated" as in the point where a current flashlight model (especially if it is the same brand name) of equal price point and quality level will be a very noticeable step up in performance and capabilities and/or you can get the same performance and capabilities level at the same quality for a noticeably lower price point. From what I have seen over the last decade or so where I have been using LED flashlights that point seems to be reached every two to three years or so which is about how it works with computers as well.

Edit: Also, on the heat dissipation issue there is a way to alleviate that issue that I'm surprised some of the better flashlight companies haven't started using yet. They need to cut cooling rings into the aluminum of the head when they lathe out the head piece and then put a ceramic thermal separator ring between the head and the battery tube. Basically using the head as a thermally isolated heat-sink with cooling fins which should cut the cooling problem in half or so and keep the handle cool to the touch and keep the head from becoming dangerously hot.