Generally speaking, if you want to maximize the off-time battery life, you want a mechanical on/off switch and not an electronic switch. However, for lights that take 18650's (slightly bigger than the 2xCR123 lights), there's a lot more mAh to waste if needed (2xCR123 is around 1200-1500 mAh, 1x18650 are 2800-3800 mAh).
I've got all sorts of flashlights from Malkoff and SF to the cheapies like Coast, Eveready, and OT (Wallmart $1 lights). Although I have specific roles for different lights, two of my favorite task lights that I've actually used for 1 plus hour tasks are:
Small form factor: Streamlight Macrostream (uses prorpietary 14500 li rechargeable)
Small/medium form factor: Fenix LD30 (18650 li rechargeable) - much longer run times ar similar light levels
Two downsides for both lights are they can't tailstand (switch on end), and they are relatively floody, so they reflect mist, rain, snow, smoke back at you if you are in those environments. Preference to the Macrostream for the weight if you like to clip the flashlight to your hat brim. Preferenc to the Fenix for longer run times, brighter output, and a side switch so you don't have to turn the light off to change modes.