I respectively disagree.

1st rule: Don't live in a target area.

2nd rule: Maintain a decent Intel system.

I'm in DefCon 4. That's very easy to maintain indefinitely.

DefCon 3: Easy to attain and maintain for long periods of time.

DefCon 2: Easy to attain and maintain for short periods of time.

DefCon 1: Easy to attain and maintain long enough for the situation to peak and either it will quickly ease up or it goes for broke. Need will dictate one's endurance.