perfect! okay so now that we got that all cleared up. your question was "how long to keep it on 12/12 cycle ???" the correct answer would be.... you keep them on 12/12 until they are ready for harvest. flowering times depend on the type of strain and some other factors as well. Your looking at probably 8 - 10 weeks before they will be ripe.i had them under light 24/7 for 6 weeks
that's pure insanity!you said it was possible to do 12/12 from day 1 and get some nice buds