I would recommend "marijuana botany" by robert connell clark or "the cannabis grow bible", also "marijuana question: ask ed" by ed rosenthal or his "marijana grower's guide", all good books. In nature 12/12 is not possible in many climates for cannabis to fully flower. At 12/12 the frost season is in effect. It is an ideal condition that indoor growers are able to provide. Others triggers naturally occur outdoors as well, including the onset of colder weather. You couldn't permanently keep any strain in a vegetative state. The plant becomes sexually ready and sensitive to any change in the light cycle. As the days begin to shorten they eventually fall into a tolerable threshold for them to flower. Generally mid july to mid august (14/10). Peace