you can do either, there really are two camps.. the 24 hour camp and the not 24 hour camp.
I'm really a fan of letting them have a dark cycle. They utilize carbs that were produced during the day without having to deal with the lights and switching constantly between respiration and transpiration. Plus, it gets dark at night. or at least where I live.
You CAN do 24, but its kind of a waste of electricity for cuttings. Just keep them moist and don't stress them. Also.. and this is the hardest for newbs, just leave them the FUCK ALONE. If you just have to touch them, wash your hands first.
good luck dude.