I have logged about 2 hours on the JC5607, with not a single hiccup. I run it on 3 X 18650's and use the AW softstart. I NEVER start it on high, and always start in on low with the soft start. Based on LuxLuthor's charts, the bulb is at the end of it's life. At $1.15 each, I will just replace it with a fresh 5607. I don't want to push my luck with a KT4 reflector. But I will keep the bulb and use it in my TLS turbohead. I would personally not be willing to try the 5607 with 6 x IMR 16340s. I would, however, try the 3 x 17670 holder in the M6, as long as you were also running the AW softstart. I would not try it in the M6 with a clicky or the stock twisty/mementary.
Honestly, I bought 50 of these bulbs, and 11 of them were not centered perfectly. Since you don't have to actually center the bulb, I can bend and twist the bulb until the filament is centered. If you think about the X, Y and Z axis, tilting the filament actually shortens the length of the filament, making the hotspot less elongated. Not quite the look of an axial bulb, but you get the picture.
Finally, I would love the ability to purchase the FM1909 bulb, but I don't want to be force-fed a new host in the process. I am sure the cost of the bulb has a great deal to do with his decision to only sell the 1909 with the hosts, but a roadblock nonetheless. for now, I will continue to use a $1.15 bulb that puts out 2300 lumens of beautiful incan light.
You know, I have spent many many hours reading this site. I bet I spend 4 hours each day just reading. I have a feeling that there are some here who are bashing this bulb because it may be a direct competitor to a (although better) bulb a well-respected seller and fellow CPF'r is selling. I think we all have seen it a few times when members post in other members' sales thread to help them get an item sold. I have done it a few times myself. So far I have only seen one verified catastrophic failure, followed by a picture of the supposed damage. everything else is heresay.