Eboni may be different to Cone PZ inks. What I found was that pigment settles in the lines and no amount of shaking is going to fix that. I rely on my printer producing the same print each time I print. I do that not by looking at prints but by measurements. That's also why I abandoned my 3880 and went to an R2000 with no lines and agitation every time the head moves.
I suspect that lots of folks are unaware of the effects of sedimentation. You need to measure it to really know. Even on a 3880, you need to print quite a lot to avoid sedimentation. If, like me, you don't do a black swap regularly, be prepared for a real surprise when you do.