I was looking into solar powered flood lamps to illuminate a sign. I noticed many had specifications & reviews suggesting that they would maintain a full power setting for only 3 hrs. Or, they could go to a reduced power lighting for 5 hrs. Reviews indicated the reduced power output was similar to a "full moon" lighting, which is not what I'd be looking for.

So, is anyone using a solar powered flood lamp(s) that they can say will last all night, including the winter months? Or, is it financially impractical for such an application?