That is sort of true. Definitely over something like Ubuntu with fixed cycles and often unreliable version upgrades. But I think NixOS is never re-installing on the next level.

But after about 5 years I would start having problems on my Arch installs and realize that some config I edited years ago is now causing a problem. I have to see if I should revert to the default config or merge in changes and if I need a new workaround. Overall the system was just accumulating cruft that ended up biting me. I never knew what configs I had edited and what the default was, experimenting was annoying forms of backing up the config, making changes and then figuring out what I actually changed.

NixOS is completely different because all of my "customizations" live in a Git repo. I have change history and it is trivial to remove things that aren't needed anymore and know I did a clean job. The concept of a re-install even doesn't even make sense. Every config change or update is just as clean as a re-install would be other than "state" like a database or my documents.

There are definitely a lot of differences between NixOS and arch such as many packages requiring patches to function at all or as expected. But "never reinstall" was a significant part of my ramp from Arch to NixOS.