I've been using
this light (Riorand Cree XML T6) for 2 years now with
this spreader lens (for Magicshine type lights). I had one for a year before that, but the wire went bad (most likely because of how I had it wrapped around my frame). I bought
this battery (8.4V 6600mAh) to go with it at the same time. I get 4+ hours with typically 50% on flash and 50% on medium. I'm skeptical that the batteries are actually 6600mAh, but they work for my needs. The only part that has failed on me was the cloth battery case to hold the battery to my frame. It still works, but is held by a lot of tape.
I've thought about getting a real Magicshine, but if I assume a 2+ year life on battery and light, at <$40 combined, it looks cheaper to keep buying the clones.
P.S. I should mention that I ride all year, all weather with that setup and got that lifespan.