I'm using Debian testing in my daily driving desktop(s) for the last, checks notes, 20 years now?
replyServers and headless boxes use stable and all machines are updated regularly. Most importantly, stable to stable (i.e. 12 to 13) upgrades takes around 5 minutes incl. final reboot.
I reinstalled Debian once. I had to migrate my system to 64 bit, and there was no clear way to move from 32 to 64 bit at that time. Well, once in 20 years is not bad, if you ask me.
I've had a couple outages due to major version upgrades: the worst was the major version update that introduced systemd, but I don't think I've ever irreparably lost a box. The main reason I like nixos now is:
reply1) nix means I have to install a lot fewer packages globally, which prevents accidentally using the wrong version of a package in a project.
2) I like having a version controlled record of what my systems look like (and I actually like the nix language)