Several hours off a Mag-LED is an understatement, those things run for a few dozen at least, and that was from a test on a 2D version. They run a bit pricer than these rechargable deals, but do understand, a few dozen hours of light is a bit better than a couple hours with a moonbeam lens.
The Nite Ize drop-in is a slightly cheaper, but probably more sensible choice. Their packaging hints at a hundred hours off a 3D...Heck, even if it's just fifty that's still a dang long running light. Not the brightest around, but it's still great in a blackout and is much more durable in a Mag body than any rechargable ever made.
Either way, it's going to be more expensive than a rechargable. If you absolutely must have a light in each room of the house, go with something smaller and cheaper like some Nite Ize MMs or a some River Rocks if you live near a Target.
I admit, I do like the idea of the simple plug-in nightlights that turn on in a blackout. As fixtures rather than handhelds, it'd be nice to have a blackout where the night lights click right on when the power goes out. Easier to find more lights and get ready for a long-term one.