Just thought I should mention this here... so I noticed that, over time, it seems like more and more of my c60oo sticks to the bottle in little clumps (C60 aggregates, presumably), mainly because the surface area available for such adhesion increases as the bottle drains with use. So I've started shaking the bottle before each dose. It seems to me that this might explain some of the waning effects with time (but is probably not the primary explanation). In other words, the inside of the bottle acts like a "magnet", pulling C60 out of solution/colloid.
It might be the case that the oil is oxidizing, although that seems unlikely. I really don't think that you're seeing c60 being pulled out of solution. It's not actually in solution as c60, but rather is chemically bonded to one of the fatty acid chains on the olive oil triglyceride. One way to solve this problem of junk formation (which I've never observed, personally) would be to split a fresh batch up into smaller containers representing 2-4 weeks worth, and freeze the ones you won't be using for a while. You might be seeing an artifact of frequent bottle opening. Storage works better if you dose less frequently with correspondingly larger amounts.