What to do with expensive data when reinstalling instead of upgrading?

Rather than replying to Syg00's contribution in a different thread, I am creating a new one to avoid changing the original thread's direction.

Reinstallation preferred to upgrading:
Quote:

Originally Posted by syg00(Post 6081039)Over many years I have come to the conclusion that it is not worth wasting too much time trying to subjugate package managers - including Fedoras various incarnations. I quickly become jaundiced and simply re-install clean and re-install the packages I need. Pays to have a separate /home partition/lv BTW ...

That's insightful, but it's not only /home but also /etc, /srv, /var etc., right? For example, how do you handle a heavily configured system? Copy the original /etc/ over the newly installed OS - would that work? How about /var with databases, web sites, DNS server configuration and whatnot?