I'm doing 23-25 miles a night on my commutes home. I run a Nightpro. the guys at the LBS recommended them for a hard corp biker like myself. Suppose to get six hours out of a charge, but I haven't tried it yet. I do get 1:45:32. It's a nice piece of equipment that I can change from one bike to another. It is a totally encased unit, so you take it off and plug it in, just got to remember to take it with me when I leave for work.

On my 10 mile commutes last year I was using a night stick, and then switched to cateye LEDs, which for in city lighted streets were effective. I used them to be seen not see.

Will have to see how the Nightpro holds up this winter with the energy sapping cold.