24/7 all the way. i always am beating a dead horse when i say this but there is no reason to not go full 24(except with autos). some ppl say roots develop more under 18/6 but others have told me it has no effects on root growth. i know for a fact though that 24/7 is roughly 33% faster growth rate. a lot of people try and argue and say plants need a rest period, they get a rest period in nature and humans require rest and blah blah blah. this is not always true. for one you cant compare plants and humans as far as rest, they are very different. some plants do indeed need a rest period, however marijuana does NOT need to rest. you dont really save on electricity going 18/6 cause you will take longer overall to achieve the same results as 24/7.