wanderson:
......... I ran a 300ma constant current Luxeon LED with well over 5 amp pulses through 10,000 cycles without a failure. ......
This is a very simple minded approach to circuit design. The fact that you did not destroy your LED does not mean that you did not severely damage it. The damage will have occurred and will show itself in two ways:-
-
A shortening of the life of the component, in other words it will fail sooner than it otherwise would. This is due to the mechanical stress on the chip's bonding wires causing eventual fracturing and depletion of charged carriers in the semiconductor substrate. There is also a problem of localized heating when the thermal conduction will not allow enough heat to escape to prevent over temperature of the junction.
-
A reduction in the maximum brightness of the LED. I know you will say it did not reduce in brightness but if your only measure is your perception of how bright it was then that is hardly very objective. It is well known that people can't remember the brightness of a light over a few seconds let alone several months. To properly test this you would have to make carefully calibrated measurements with specialist equipment.
No one is saying you have to have a resistor but you have to have some form of current limiting even on a very narrow pulse. It is better if that limiting is under control rather than the vagaries of a particular component.