JCD, you make a decent argument for keeping the incandescent bulb. However there are certain provisions to make it a winable argument.
1. The incan version of the 3D light only runs for 6-8 hours. With brand new3 batteries at the start of a power outage, that may buy the owner 2-3 nights of light. Assuming that the batteries are fresh! What if they are servicable, but at only 75% capacity? Then they are looking at maybe 2 nights, and just a glowing filament on the third.
2. "Always haveing a fresh set of batteries available is important..." I fully agree, however, I suspect that most people, do not have spare fresh batteries.
3. "switching to a 2P LED form factor would be far outweighed by the significant decrease in usefulness of the light emitted" I compared the 3D maglight with the incandescent, to a 2D rayovac LED. Indoors the light is different, primarily by tint. Outdoors, the mag has greater throw, and reminded me of why the maglight was the best, in it's time. For everyday indoor chores, the difference is negligible.
IMO, the difference in run-time is really significant. Back in the day when all lights were incandescent, more often than not, if one picked up a flashlight to use, the batteries were half dead. Afterall, they really only had a 2-3 hour runtime on carbon batteries. Alkalines picked them up to 4-5 hours. With an LED we are talking about a ten times improvement in run times.
So let's consider a 3D mag. After 4 hours of use (incan) it will be at 50% capacity, yet at 4 hours use (LED) it will be at 95% capacity. The incan will have a demonstrabile decrease in output, and the LED will not. For the next couple of hours the LED will have an output advantage. (until you change the batteries in the incan) provided of course that you have them, or they are obtainable. IF NOT... then the incan is dead, and the LED has 70 hours of useable light.