plants grow both in the dark and in the light. When a plant is flowering it stores up its energy during the day, and at night is when it does most of its growing, but during veg, its growing all the time, wether its light or not. I have a 600w MH that ive been running nonstop for 3 n a half weeks now, n my plants are thanking me for it man. Theyre fuckin beautiful, straight up. 24 hours of light is beneficial IMHO. turning the lamp off for 6 hours dont make a damn bit of a difference, and youll only save like 5 bucks a month on your electric bill.
n LOL @ you guys sayin that youll use your growrooms for heat during the winter -- this is actually a realistic fuckin idea for that one particular room. Fuckin temps outside are like 30 degrees, but its fuckin 82 degrees in the room im growin in, allllll the fuckin time. Sometimes its TOO hot in there man - id rather run my heater and be able to control my temps in the apartment. If you eat/sleep/shit/live in your growroom though and the other rooms dont make a shit of difference to ya, you could probably save mad money on your heating bill if you just turn that fucker off n use the heat from your growlamp, lol. HELL, id even be inclined to think that if you live in a small enough space, and leave the door to your growroom open all the time, you could probably spread that heat around through your whole apartment, and not have to worry about heating ever again in the winter, lol.