Are they temperature controlled?
I'm running mine at 1A now and getting roughly 980mW from a cold start (after Hi-Power lens).
As it warms up, the power starts to drop 1mW at a time. At the 2 minute mark, the power is about 920mW. After 3 minutes, I lose about 100mW from start-up. The case temperature is slightly warm at this point. The power settles at about 870mW after 4 minutes.
Keep in mind that this is a portable unit, so heatsinking is not optimal.
I have not had the chance to test my second diode yet, but I think that the diode I am running now is not one of the "higher efficiency" diodes.
This diode seems to be very temperature sensitive.
I will need to get a IR thermometer to make any "scientific" observations...