I'm slowly but steadily working through all of my miscellaneous pens. I currently don't have one full set of colours from the same pen brand, but more of an erratic collection of misfit pens. What's quite good about this scenario is that I'm using more of an odd range of colours and being restricted to some of the lesser used colours means I'm a bit more inventive and a bit more chaotic - which is always useful.
The mismatched pen collection also means I'm using pens of all different sizes, thicknesses, opacities, and scents (yep, I still have a couple of scented felt tips), so I end up being a bit more unpredictable and strange from all sorts of different angles, and ultimately I think that's the best. It's quite subtle at times, but I feel a difference in how I approach drawing. It's somehow more satisfying to me to have a jar of miscellaneous pens than a neat matching set.