it all depends on ur grow space, plant genetics, lights... At 8 inches ur gonna have roughly about a 1 foot tall plant when its finished,. which is pretty small. im not sure what ur grow space is like but mine iesnt all that big ans i grow them out so that they are just barely touching the lights which gives me about 1 foot of vegg room and 3 feet of flowering room with the hps. If u have a giant area, then 8 inches would be a waste for sure though