If you have the space in your grow-room to rotate them, then yes I think it helps in the long run to evenly disperse the light - both in veg and straight through to the end of flowering. It may become a bit more difficult to do once the start to really spread out and get top-heavy, but I usually use a bamboo-stick stake to support the tall colas in that case... Check out my latest grow for some pics to see..

Bagseed & Barney's Blue Cheese - Marijuana Growing