Kaya666answered grow question 6 years ago It all comes down to personal preference. GrowWeedEasy suggests an 18/6 light cycle but acknowledges that there's no scientific proof autos need a dark period. Now, anecdotally my plant seemed to perk up & look great after a 4 or 6 hour dark period so I choose to do 20/4 in veg & 18/6 in flower. But other growers report success with a 24/0 cycle. As long as your grow space is staying cool & you don't mind the additional electric costs, there's no harm in 24/0.