How do you organise sketchbooks?

I've noticed that people have many different ways of organising (or not organising) their sketchbooks. Some artists work through one at a time, others have several on the go at once. Some go back over their sketches and 'finish' them, others would think that a sacrilege of the very concept of sketching. Some artists rip out pages and file them, others keep each sketchbook intact.
Is it possible, or desirable, to organise the content of your sketchbooks?

Here's my approach (which may change next week!)
I have several sketchbooks on the go at any one time. There's always a moleskine (or moleskine ripoff as I'm a bit stingy) in my backpack and usually an A5 wirebound sketchbook as well. I always have at least a couple of pens and pencils in my backpack, and usually also a pencilcase with eraser, sharpener and more pens and pencils.

I keep all my sketchbooks. Here's my collection of full sketchbooks:

(they do say 10,000 hours makes you an expert - I think I've reached around about 7,000...)

These days, when I start a new sketchbook I leave the first page blank. When it's full, I write on the front page a summary of the dates, places and subjects of the sketches in the book. It helps if the front cover is transparent.

Sometimes I rip out some of the sketches and file them by subject. I generally don't care when they were done but it's useful to file sketches of musicians together, or water birds, or the Grand Canyon, or I might file them under musicians in Canberra, or waterbirds - sea and waterbirds - freshwater. (I'm an ex-librarian - subclass cataloguer).

Anyway, I file the sketches along with some printouts from some of the photos that I've usually taken while I was sketching. When I'm ready to paint the scene, I can choose one or more sketches and photos to work from. I use manila folders, with the edge folded up to make a kind of pocket, and I staple a photo or sketch on the front of the folder to make it easy to identify.

Here are some other people's approaches which I found interesting.

This artist describes her sketchbooks and journals as an obsession that she doesn't want to be cured of:
'How did they multiply like this?'

Joseph Stoddard goes back to the sketches, finishes them and adds photos: