Who ever you choose.

Here is why I say 24/7

During the dark cycle the plants release hormones. As the seasons progress the hormone levels get higher and higher during the night and are broken down during the day. The plants seem to get burned out after a few years on this regime. Zandor is one of the best growers around and uses 18/6 and chemicals. His mothers last five years untill they die. Organically feed mothers on 24/0 can last decades. It is either the chemicals or the 18/6 that is doing it and really who is to say untill it is tested. Since no growth is done during the night and hormones are released which is how the plant knows when to flower, I say just keep it growing and it has always worked for me. With a larger setup you could save a bit of power running a 18/6 but I would rather trick my plants into thinking it is still there first day of life.

When regenerating a plant, as many leaves as possible are kept on the plant and it is put back into 24 light. After the hormones are used up the plant begins veg growth again after about 1.5 or 2 weeks. I have never tryed to regenerate under 18/6 so I can not tell you how it works.