lol... Preventative maintenance primarily... Those fans start to yellow, wilt, and wither into the plant. If you don't catch them, that decaying plant matter can feed all sorts of things you don't want growing in your room. Secondarily, increased light penetration... The light can penetrate all the way to the bottom of the plant, for full bud development up and down the plant.
You just have to create the optimum environment, and the plant will grow itself. The plant naturally diverts energy to the buds in late flowering, that's why the fans die, naturally... Unless they're loaded with N... So since the roots are full of starch after 4 weeks, the fans aren't needed... Take them. Hardly anything is stored in the leaves. The guys that think this makes flushing the plant easier are wrong. If you don't flush, you're buds are still gonna burn like shit. That shit is stored in the roots!
I really wish everyone would go to their local community college and enroll in Biology 131. (not trying to be an asshole here, I'm serious. It answers a lot of questions.)
The leaves are used to take light + nutrients pulled up from the root zone, and convert them to sugar (starch), which then goes through another series of chemical reactions, traveling through the plant, and being stored in the roots.
The fans changing color depends on the particular minerals that remain behind in the leaves... anyway... I think I answered the question.
Great job otherwise. Looks dank.
We're not so different from our plants. 
