You would be better off using NiMH than NiCad. I use NiMh with my LSH-S. Runtime on NiMH is at least twice that of NiCad, but still less than Alkaline AAs. Best runtime is Lithium AAs: 5 hours in Sun mode.
I use 1800 MaH NiMH AAs in my LSH-S and rev1 LS. I even did an impromptu runtime test with the rev1 LS and 1 NiMH AA, and the total runtime is something like 7 hours. Those who were in cpf chat at the time remember me calling it my magic battery.
It will Run for over 4 Hours at Full brightness on 2 AA 2100mAh NiMh Cells. This is a first run ARC though so the new version may not last quite as long as it draws slightly more power (and is brighter).