Light is not a big necessity for clones, i keept mine in my garage for days so it had a lot of dark times., i did keeep it under constant moisture and had no problems, now i have seen people advise against using HIGH power power lights for clones, so the minimal the better
flourescent blue spectrum light on 24/7 and a few drops ofsuprthrive in your water will encourage rooting the cones in soil... a good cloning gel or powder also helps.
Good amounts of light is essential for all stages of growth. The plant makes its food with the help of light. I usually keep mine under a T5 fixture with a schedule of 24/0. But, temperature and humidity are the number one priority. If they get too hot, I will drop them onto an 18/6 and have the lights off during the heat of the day.
I think DLtoker hit the nail on the head. I keep them under 24/0 CFLs just to keep the temp constant. In the winter months I get a huge swing. The temp in my cab is 27c.