These runtime plots are for a Fenix L1P v2.5 1w LED flashlight.
Equipment used is a Extech Mdl 401021 Light Adapter into a Radio Shack 22-805 multimeter with a PC interface that is using Scopeview software (V 1.08).
The vertical axis is in mVDC and is equivalent to one footcandle @ 1Ft oer division. The horizontal axis is in minutes, 30 min per division for the Lithium plot and 15 min per division for the Alkaline plot.
Be aware that your actual battery milage may vary from that indicated by this runtime plot.
The runtime to 50% max brightness = 3 hours 10 minutes for this plot using a Battery Station 2900 mAh Li-Fes2 AA battery.
The runtime to 50% max brightness = 1 hour 51 minutes for this plot using a Ultra Alkaline alkaline AA battery.