Do you ever disable the "auto-update master page" setting?

No. Can't see why I should... If I want to clear it's fast done with C/Alt and dragging my finger over the buttons, or just change page.

I've never had a reason to turn it off, so I haven't !

No. Actually, in the beginning I even didn't know about this checkbox and had a pretty hard time finding out, why masters are not recordet after reloading the show. What is the original purpose of this option?

Tomas, Its a good option for live events and concerts. You have the ability to lock pages down so you can busk away with your masters live, moving presets, effects, channels and sequences on the fly but always able to get back to a known starting point when the next song/event starts.

Its also useful when you are recording pages to sequence lists so on playback it appears exactly how you intended. (ie. if you want sequence step 1 to load page 1, its a good thing to have that page 1 to be something intentionally recorded and not easily changed by accident)

OK. Thank you. Some experiments ahead of me. First curiosity: does it apply to Congo Kid too?

Yes.
Congo Kid has all of the features of the larger Cobalt platforms, the only differences are the maximum desk channel and patched output counts.

The other thing to keep in mind with the Congo Kid is that you do not have the display screens in line with the masters. While you can move things around if you want to, it can get confusing quickly. You do have the masters dock so you can see the info, but bouncing around is not as quick and easy as it is on the larger desks.

On a Congo kid I usually don't mess with pages or ranges at all.