The 4D is a fluorescent, so it wouldn't last as long as you are thinking.
Yeah, the package said 40 hours continuous runtime, I think.
Also forgot to mention mine now has Dorcy Gelbrites in different colors, a Dorcy Gelbrite package with the 2xD and 1xA, the Energizer "Find Me" 2xD with blinking red LED, Energizer torch/lantern flashlight, and the Nite Ize LED/switch combo for $9.99. And a few other things I can't remember right now.
I was on my way to work, and only had a few minutes, so my head was literally spinning looking at all the new stuff!