Lights: Burn Time to Lumen Ratio

[cloudwalker_3]

Can anyone recommend some front lights that are bright but that also have a long burn time? I need some serious lights for the Dunwich Dynamo this year. A couple of years ago I rode it using two 5 LED front lights and they were not really good enough once we got into open country.

I'm aiming to have two lights mounted on the front for extra brightness.

Thanks.