From 24hrs to 18/6

When do you decide to go from 24hrs of light to 18/6?

Thanks for any response
oh yeah check out the jorny https://www.rollitup.org/newbie-central/274981-1st-grow-1st-journal.html

I never use 24 hour light. I use 18/6. As far as switching you could do it pretty much anytime. It grows fine with 18/6.

i went after two weeks. i was under 2 x 55 watt cfl. used same lights for 1 week on 18/6 then moved to 600 watt hps. plants looking good.

i always switched from 24 to 18/6 at around two weeks.. but i just read this good article in cannabis culture that the author was saying that there really is no need for a dark period in mj during its vegetive stage, and that plants grown under a 24 hour light schedule will grow 33% faster than those that are grown under 18 hours of light.. i am not positive of how true the article was, but it all kinda made alot of sense to me and made me wonder about the thinking behind an 18/6 schedule... i now wonder if people do the six of for cost reasons, or if heat build up is an issue, and the dark period would allow grow rooms to cool down some... but other than that, i don't really see the need for a dark period after reading this article..
i think if you just google does marijuana need a dark period you maybe able to stumble across the article that i am talking about.. it was in a cannabis culture magazine, not sure what issue, but i just found it by googline the dark period ?..

Thanks Guys!!!