Ran out of disk space, want to run another service, want to check if there's any software updates.. I don't know, in my case I had it in a moving box for 1.5 years and I was pleasantly surprised it even booted and immediately started serving up stuff to my TV.

If you were happy with it and need to do it again? If there were small gotchas you aren't eager to rediscover?

that actually sounds WONDERFUL.

I had a machine that I let run with an old (private) certificate for years because I didn't remember the how and the what of renewing that specific certificate.

I had another machine that had a hardware failure, and I spent an enormous amount of time recreating it.

I have been running a personal server (FreeBSD) for close to 20 years now, and upgrading in place since 4.6. And once some hardware components fails (especially disk) I spend extra time figuring once again how I did it then. Having everything described in a configuration would take less time to do such fixes.