Great reminder, Centaurus, of a potential killer.
This is why I always check the 'air con and press' system in the climb, passing FL100 and FL200, no matter how automated the system is.
In the Helios accident, I always felt that Boeing should accept some responsibility for having an identical warning horn for 'take-off config' and 'cabin altitude' warnings. I wonder if the Helios crew thought that the audible horn was a false 'take-off config' warning?