Ya know, I usually leave my fan leaves on unless they start to yellow or just look less effective than the underlying leaves. I tend to think of 'em as big solar panels (?). My understanding is that it's the leaves (and not the buds themselves) that are responsible for the photosynthesis, so I don't really feel it's necessary to have the buds exposed to light, but rather you should maximize exposure of the foliage to your light source. I could be wrong about that, I dunno, but I always try to keep leaves that are healthy and gathering light, and usually only trim them if they're unhealthy or damaged or just aren't really doing much cause they're too shaded. That's not to say that I've never purposely removed fan leaves, I def have when they were in the way or whatever, as long as the plant has enough other healthy leaves to compensate, then it's fine to remove some fan leaves, it'll do no harm.