Time of useful consciousness at 35,000ft is not in seconds. For a start you have a lung full of air, CO2 and water vapour and that will see you OK for quite a time. I can't remember off the top on my head but we used to fly with cabin altitude at 39,000ftand you could certainly drop your mask to blow your nose. The rule changed above 40k and you were down to seconds. IIRC it was something like 20-30 seconds at 45k and you had to initiate a 5k/m descent with a minute. Higher still with considerable overpressure (and you would have had a mask on) you had 30 seconds to initiate the descent.