I always do this now. With both phenotypes of Ice, they start showing hairs about 5 or 6 days quicker, and finish 5 or 6 days quicker. I have just switched them to 12/12 and let them go, but it takes longer and doesnt yeild any more for me. Why not do 36 hours darkness to get them going. I have never had a hermie or less yeild from this. I learned of this by accident when a wind storm knocked out power for 3 days. Had yeilds that was the same as the last 4 or 5 grows, just quicker. I suppose it could give some strains some problems...not sure. I do believe I read somewhere(serious seeds website ???) that they recommend 36 hours darkness at the onset of flower.