I carry Lithium in all my EDC flashlights. The flashlights must be able to operate in the cold. I'm experimenting with rechargeable Li-ion because of the high current they provide, and my flashlight must be brighter than yours. I don't have any experience with NiMH. It's good to hear NiCd batteries are good if you take care of them, but I personally have had bad experiences. Meanwhile, there are other options that are not as high maintenance, while still performing well. Alkaline batteries have no place in flashlights I carry away from home, unless there's no other choice.