I don't object to any of this. "Restart this system from initial state" is quite a bit more common than people imagine in CL. I was hinting at it perhaps being even more common than image-based development, though don't quote me on that. I personally don't even really create Lisp images in dev (save for creating executables that I don't then further modify, which are technically images in SBCL).

Incremental runtime modification is great for development, but I very frequently restart (from sources) every so often, and certainly at least before deployment to verify everything is working as expected. Sometimes because it's completely necessary, sometimes for my own sanity.

For production, I think it's a very "neat" thing to be able to do and I've heard some great stories (no personal experience), but it's definitely a foot gun if not used very carefully.

Can you explain how you sync back to code, in practice?

In other words - if you modify the run time, are you then able to mirror those changes in your codebase and then reboot?