Normally, once in the morning and once in the evening. (Arch Linux) At the very latest, once a week. Why? Well, updates are important, and with a rolling release distribution, you get them when they're ready, which means multiple package updates each day. I sometimes skip the morning update if it's a huge update or if I need my system ready right now. My update process is scripted, but every action is still triggered manually (to remain in control during the process, also to answer any installation-related questions that might happen). When I type "_u" (I use the underscore as a leader character for several custom functions), first a regular pacman update from the Arch repos is started, then an AUR packages update (I don't mix both), then flatpak, then fwupdmgr. Also, there are several pacman hooks which also automate some things e.g. deleting old packages from the cache or displaying whenever there are new .pacnew or .pacsave files lying around. The whole process is very fast but still admin-controlled. If I ever see a problematic update, I can skip or delay the update. Also, I can always roll back to a previous btrfs snapshot if something breaks.