My bad on the D cell stats. I went back to the spec sheet for a Duracell Coppertop (because how many folks buy premium D cells for their flashlights?) and the curve I was recalling is actually a 750mA curve, although the exact same color line on the AA spec sheet is used for 250mA, so I guess that's where I got them mixed up. It's not marked on the D cell graph but at 250mA, a D cell should last way longer than 16 hours.

Just curious, how many ETSers out there buy premium D alkaline cells for their flashlights, like the Duracell Procell? Just talking D cells, not CR123, NiMH or other types or sizes of cells.