I think your 2 hour runtime for a P7 is a little high.. Most P7's run around 60-80 minutes.. I have found that the new Ultrafire Protected 3000mah cells have given me the best runtime w/ p7 flashlights..
The gradual dimming w/p7 flashlight is very relevant to what you might need.. The MS light is a constant output over the 3 hour runtime, you need to take this into consideration..