Actually oxy generators can be purchased with longer burning times - 22 mins is one type that I am aware of. Also, bottled oxygen is an option on our aircraft with an endurance of up to two hours. It is convincing the owners of the necessity to have sufficient passenger oxygen that is my first hurdle, which is the crux of this thread.
So, ironbutt57, can you confirm that you fly over the Rockies in an aircraft with 12 min passenger oxygen endurance, using escape routes? Or was this a general comment?