Completely understand your point of view - especially since I like to tweak settings until everything is exactly how i want it. However, I force myself to do a fresh install with every major release. It’s much less painful to do with Linux (and even less with Qubes) than you might think since most (if not all) of your customizations will be in /rw. Also, you can wait until both Qubes & Whonix have major releases ready.
Some reasons why I always do a fresh install:
- In-place upgrades have much more variability than fresh installs and thus, are much more difficult to test as thoroughly. For security distributions, you don’t want to be the experiment.
- Hopefully, I’ve learned something since the last major release and will be that much smarter configuring the new system.
- Lots of software installs might mean accumulated crud. And software you no longer need.
- You can never get enough practice with backing up and restoring.
- (EDIT) Knowing that you’ll be performing fresh installs regularly keeps you more disciplined - to take notes, and to avoid unnecessary changes to TemplateVMs.