I currently have 6 (2x sets of 3) Nova 5 Star LED heads spaced around my darkroom (all aimed at the ceiling from a distance of 12") which is 6' x 7' for the present they stay on, but that is only until I get around to wiring a 2 way socket to the Stopclock Pro Timer. I have tested them on full power with Ilford Multigrade IV paper and get no discernable fogging even after 20 minutes with a 'max flashed' bit of paper.