dont use plant lights unless they are fluoresents, the ones your talking about are halogen(incandesent) right? those lights are pretty worthless, they arent worth using. get some cfls, 6500k for veg and 2700k for flower. they put out much more light using the same wattage as the plant lights. how long if you kept it w/the crap light? i'd guess 7-8 months and you'd probally yield a quarter when dried, if all goes well maybe a half dry.