Search vs. Tagging vs. Notebooks in Evernote for GTD

I use Evernote to organize my action lists and other checklists in my Getting Things Done (GTD) system. Recently during weekly review, I was thinking about long-range planning -- what David Allen calls "Horizons of Focus" -- and I decided to add a series of notes to Evernote containing my current thinking on them.

I put the new notes in my existing notebook called "Reference". The problem was, there are many notes in Reference, covering everything from lists of movies I want to see to what kind of batteries my devices use. I wanted these new notes to be easily accessible during Weekly Planning. But how could I best group them together so that I could call them up conveniently?

My first thought was to create a new Evernote tag, .Planning, then tag all the notes with that tag. But then I realized that would be time-consuming, and wondered if there were other ways to do it.

The next thing I tried was simply naming the notes in a consistent way. I started each of the notes with the string "GTD", such as "GTD Horizon 2: Accountability (Roles / Responsibilities)".  Now I can search for "GTD" and all the related notes popped up. This requires discipline to maintain: I have to remember that for a note to be in this group, I have to start it with GTD.  If I forget, the search won't find the note. Plus, I have to be sure to keep hard edges: to NOT use the word GTD if I don't want the note to be lumped in with the others.

In the end I decided to create a new Notebook called "Planning", and transfer each of the "Horizon" notes to it. Then I could review not only those notes, but other planning related notes as well.  All would be quickly accessible regardless of naming convention or tagging, as well as via search, and it would be easy to add a new planning-related note.

There's nothing wrong with any of these three approaches. In each situation, you can use the one that seems to be the best fit.