I ran a 5,000 lumens SRK style 5X (Fing below) light for 2 1/2 minutes, and it began to get warm/hot, but this was a well heat sinked modded light, so the idea is to get the heat to the outside. Can't really compare a 12K-15K light (4K-5K per XHP-70 LED) that Mike C built with what we are talking about. He's pulling 15A at twice the voltage, equal to 30A from 4P cells. No idea what you are trying to say here, or compare to, but Mike C's custom build is wayyyy different. I can't find him mentioning cells, but the only way I see that working is with up to 8 18350's, so about half the capacity of 4 18650's we got here. Besides getting hot after one minute, the cells would probably deplete in 10-12 minutes, if I did the math correct.
Just for comparison purposes:
A SecurityLng SF55 4X SRK clone, modded by replacing the LED's with U2 3C's on the stock aluminum MCPCB, upgrading LED wires, and adding some thermal grease for the contact to the large MCPCB, does:
Lumens: 2,686 @start, 2,492 @ 30secs, 22.5 kcd (300 meters)
A TangsPower Fing 5X SRK clone, has smaller reflectors, fully modded with 4 U3 3D's and 1 U4 1C in the center on Noctigons, 2.5 mm thick copper shelf, 7135 based driver, 14.66A measured at the tail (clamp meter):
Lumens: 5,134 @start, 4,910 @ 30secs, 41.5 kcd (407 meters)
A SupFire M6 3X SRK clone, heavily modded with U3-2A's on 20mm Noctigons, FET+1 DD driver:
Lumens: 5,202 @start, 4,991 @ 30secs, 65.5 kcd (512 meters)
Note: An SRK running at a stable 15A on 4 Samsung 30Q BT's would run for 48 minutes (12Ah/15A = 0.8 hours).