This question was in the Philofaxy Facebook Group. And I could answer in a second. And I should write too much to explain for what and why.
Let's start with the why!
I have ADD and I want everything perfect. I can't say no for things. So I need all the stuff and all the stuff don't fit to one (two, three) planners. It's ok, until I can manage the all the planners. I was once on a Filofax meeting...