No, haven't gotten the SF K3 hot yet. I was interested in how long it would take to heat up when I used it, but it apparently takes longer than you'd think; the cooling fins seem to work well. It may take a dedicated test to determine.

How long does it take to get the SF M3 hot? Even though the fins seem about the same, the K3 head is a tad bigger in diameter which probably puts heat build-up about par with the M3.

On the subject of high output lights and heat, there is a warning on the ThruNite TN12 to limit max output to 10 minutes. 1000 lumen is a lot of light out of such a small head with no cooling fins, so 10 minutes is understandable.