personaly i grew 5 auto big devil kept the light at 18/6 for 9 bloody weeks they ware budding fine but small at i switched it to 12/12 600 hps and in 2 weeks they doubled in bud size and ware done
i have read a lot about them and there is so many diffrent opinions some switch it to 12/12 after the 4th week others keep it on 18,6 under there 300 hps grow light
for me switching it to 12/12 was a lot better