24 hours is not that long !
I would consider long term emergency lighting to be for a month a more, post large hurricane, EMP event, or other large disaster.

A standard stock D cell Maglight runs 12 hours on a set of batteries, one set of spares gives 24 hours.
A flourescent lantern runs about 24 hours on one set of D cells.
An LED lantern for several days.
For lower level or localised lighting there are numerous LED flashlights that give run times longer than 24 hours on a single cell.

For TRUE long term emergency lighting I have a few hundred alkaline cells, a few dozen lithium cells, a 12 volt system with PV charging, a few hundred candles, and ample kerosene for several thousand hours light.
Candles and oil lamps are ideal for long term lighting but can be a fire risk. Consider installing hooks in the ceiling, or wall brackets, from which lamps can be hung.

The true doomer also keeps stocks of sulphuric acid and lead sheet in order to make lead acid batteries.