The presumption is, that after waiting a decent while for a pilot response, no response probably means that the pilots are"out of it". If the are aware, they can cancel any time.
On the other hand, getting down to breathable air should bring the pilots back into the loop, hopefully once they get back below 20/25,000'.
Not sure how long it takes to regain consciousness at 20,000' after a spell at "over 350".