Bob,
I only have experience of 2ATAF Battle Flight in the 70s. We held a 5 minute state 24/7 in the Phantom. We held the 5 minutes out of the cockpit, sitting in a crew-room near the aircraft, which was challenging during a night scramble. Our limiting factor was the INAS align that took 100 seconds. Our highest state was Cockpit Ready which would equate to 2mins. We were allowed to maintain in the cockpit for up to 4 hours at a time. Our normal duty time for Battle Flight was 24 hours, after which you were supposed to get 24 hours off.
There was a very strong directive from "on high" that we were to make our scramble times at all cost. This led to some bizarre stories, some of which will hopefully be told on this forum.