Figure out a good timing for fetching package lists and updates

I currently do a /etc/xdg/autostart/gnome-software-service.desktop on all systems since I don't want to have package going wild draining battery to fetch updates i don't care about and then kick those off manually.

While they are settings to disable automatic updates they don't seem to prevent gnome-software to tell packagekit to fetch now package lists. So i wonder: should there be a big toggle in software or GNOME Settings that allows to put updates into e.g. the night hours (as some OSes do)?

Should we only fetch updates when the screen is blanked and there's an unmetered connection?

/cc @francois.techene on the design side how that should look like?