Thanks Tarin, great advice. I'm certainly of the slacker variety, but looking to reform!
I'm often hit by strange imaginings during insight meditation, and until reading this essay felt that maybe they were meaningful, or maybe I was spacing out. After reading one of your ending paragraphs about this, it occurs to me that probably the "imaginary" experiences are both meaningful AND spacing out

For a whole day on my last retreat, investigating sensation in my thighs was inseparably linked to "imaginary" flashes of death in many forms (gore, decomposing bodies, bones, suicide, explosions, car wrecks you name it. horribly realistic and rapid-fire like subliminal television).
Same retreat, I came to what felt at the time like a very strong Realisation, that all of my fellow meditators and I were gorillas -- you know, mountain gorillas, that sit in a misty glade and chew bamboo contemplatively. We arrived at the hall in silence, explored vast territory with little or no outward sign, absorbed our insights without help from others or disturbing them, ate in silence and returned to our rooms by starlight for rest. It felt primitive in the sense of it being fundamental, something lost over the centuries of trying to "improve our situation" (read: hide from dukkha).
Sounds weird now and I'm probably not doing a great job of explaining it, but there you go. Your essay reminded me of these and similar experiences, and I found it very relevant.
Thanks!