using 24 hours of light per day will keep the plant alive and growing, usually no obvious problems, .. BUT ... the plant needs the dark hours, thats actually when they do the most growing, and processing of their nutrients ... plants tend to show males more under long light periods ...if you want to use 24, go ahead, theyre your plants, just dont whine when you find your herb doesnt measure up ... the 24 hour plants will not grow measurably better, anyway ... :smokin: