Rechargeable NiMH (Nickel Metal Hydride) will not run as long as alkalines unless it is very cold. Also NImH batteries have a very high self discharge rate. Some are 10% loss the first day. If you leave them around for a few days you will not get a full run time. For a full run time with NiMh you basically have to charge them fully that day.

See the forum thread "light selection guide" for run times, prices, and power of lights, on the market today. There are links to photos of the beams at night so you can see for your self what you get.

Here's what I use for my 7+ hour night rides.

http://www.gretnabikes.com/product.a...d=69&cat_ind=7