Plot a mental Graph, With "Time to Switch to 12/12" is a factor of plant height or plant size i.e. the Y-Axis, and Time Spent Feeding (exposure time to light) in the X-Axis. All other growing factors held constant and knowing that Plants grow continuously under uninterrupted feeding.
Say your target time to switch to 12/12 to trigger flowering is say 1/3 of target genetic height of mature plant. You will see that the Y-Axis Goes up quicker with longer, more exposure to light light.
For those who like Math, DY/DX or the gradient (slope) is steeper with more light exposure, meaning Growth Rate increases or decreases depending on quantity available food, in this case the time exposed to light energy.
Now Plot another graph with Time To reach Target Height in the X-Axis and Monthly electric Bill in the Y-Axis. Because overall KWh Expense on the Y-Axis is directly proportional to Time Spent growing, i.e. your overall KWh expense goes up with time spent growing.
So if you increase your time spent growing, by reducing feeding and therefore reducing your growth rate using a 18/6 light cycle, you will increase your overall KHh Expense.
You save money by feeding 24/hours a day. Unlike C4 Plants like corn that can take an unlimited amount of light intensity and grow Record heights in record time, Hence the saying to grow like corn or something like that, C3 Plants like Cannabis have a light intensity threshold that if you stay under this threshold and do not go too far bellow it, the plant will keep growing uninterrupted with uninterrupted exposure to light. Only CAM plants need an actual "Dark" phase to fix carbon.
Like I said earlier, the actual Dark phase of photosynthesis does not require darkness but takes place without the use of light energy whether the light energy is there or not, the process goes on.
For science buffs, remember the two stages of photosynthesis in C3 plants and the three stages of photosynthesis in C4 plants. Apparently this is not common knowledge that Photosynthesis takes place in two or 3 stages: light-dependent reactions and the Calvin cycle (light-independent reactions). Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH. The Calving cycle or light-independent reactions still take place 24/7 365 as long as light is present to replenish the Enzymes for the reactions in the light-independent reactions. The first phase needs light as will go on as long as there is light because. Like I said earlier, the enzymes of the Calvin Cycle need light and therefore by starving the plants by six hours, the plant has to rebuild this enzyme reservoir when the lights come back on. Whereas under uninterrupted light, the Enzyme reservoir for the Calvin Cycle is never depleted.
The difference in C4 plants like corn and why they can take unlimited amounts of light intensities (Watt per square foot) is that they have evolved a second light dependent process that protects the Calvin cycle from the effects of photorespiration which happens if you feed the plants too much light intensity it shuts the stomata and starts respiration instead of the Calvin Cycle. C4 plants do this and also continue to the Calvin Cycle so they cannot suffer photorespiration at high light intensities.
Remember light intensity refers to the Watt per square foot and not the length of exposure to wattage
Happy Gardening!
