Well, I've learned more about Blender, Cycles, and render time.

This is a 5-second animation, at 25 frames per second, resulting in 125 frames of animation. When I rendered the still-images, I used 2000 samples per pixel, which took me at least twenty minutes.

In an attempt to see what it looked like with the cubes rotating, I cut the normal 1080p resolution down to a quarter of each dimension, and it still took two minutes per frame! Which made the whole thing take four hours to render.
(I only have a GTX 1650 graphics card, as I can't afford anything better right now)

Fortunately, I have a Denoise node in my Composite post-processing, which apparently means I can drop my quality down to 500 (and use some very relaxed Adaptive Sampling settings), and have NO effect on the final results!

This animation took me two hours at full 1080p resolution, due to the speed-up, but that's a 32MB animated GIF file! This is just 540p, so it's just about 9MB, right under the wire for s here!

If you want to see the full-size version, it's on my Twitter page:
https://twitter.com/CarlFoxmarten/s.....70038769639425