A few of my opinions:
1. I second what jimjones3630 said about buying from bulbconnection.com.
2. I have run this bulb with 12x CBP1650s in an FM 12aa-3d holder. Get about 8 min. of runtime, give or take.
3. I do not run it more than 2 min. It is incredibly bright; one of the brightest that I have ever seen. Gets pretty hot quickly, even though I have a finned head, kiu high temp switch/holder, FM cammed reflector with heatsink.
4. Bulb at spec gives out gives out 2800 lumens (est. 1820 torch lumens using 65% conversion factor.) At 14.4 volts, the bulb lumens rise to 5300 (est. torch = 3445); at 13.2 volts, bulb lumens at 3909/ est. torch = 2541. The latter figures are the more likely ones with the CBP1650s, imho.
5. 2000 hr. life bulb ---> results in good candidate for overdriving, esp. with direct drive.
All in all, a good "wow" light. Sometime in the future, I plan to use a different battery pack with different batteries.
I have to say that after 4 or 5 runs with this setup, and my initial joy of seeing the incredible brightness, it is not my favorite. For a bright (although no where near as bright as the 64623) hotwire, my favorite is the 50W 64610 bulb with AWR's HD set for 13.0V. I get some 1300 torch lumens for about 23 min. with Eneloops.
Regards.