If you align layers along a path in After Effects, try slicing the path instead of trimming it. Since the path really gets cut at both ends, every layer attached to it re-fits itself as the path grows, shrinks or slides. No offsets needed.

Doesn't it depend on the way it's aligned/traced to the path? This looks really good but it doesn't seem to be the way the normal trace along path works. What's the secret sauce/method?

Basically pointOnPath() at evenly spaced %, but on the sliced path instead of the full one. That's the whole secret.

the path got shorter and nobody asked for a new brief.

so my offset keyframes were all pointless

Love the spiral bit where the circles keep growing