What you term my "confidence" in GD methods is simply a reflection of the fact that that's what I use. If you have a hammer that does the job of pounding nails, you don't need to go looking for another! In the GD system as I learned it, it's not a matter of "after a particular grade" -- you should be crafting your own conjurations as soon as you begin working with practical magic. Dee was of course a core inspiration here, but so was Pietro d'Abano, who held that after 50 years or so every grimoire becomes obsolete.