Having spent three years of active duty in the Marine Corps I can tell you from experience they were seated at least 45 minutes before the President's speech. Hurry up and wait is the order of the day in the military, more so at the academies I'm sure.
I can second that. In 1993 I was in the Army and was "volunteered" to go see Clinton speak at Camp Casey. I didn't really want to go, not so much for political reasons ( I wasn't too political back then) as not wanting to sit on a bus in Korean traffic for an hour but each platoon had to send 3 people and I drew one of the short straws). We sat there for about 2 hours before he arrived. The only reason we didn't sleep was because the corp commander, General Luck, was telling us we better cheer for the guy because we had to respect the office, if not the man.
I actually work for the Navy so I am sure they were there early. I have been in classes with sailors and I arrive at the assigned time; they are already halfway thru what they are working on when I get there. Mostly all the officers and enlisted I work with are on time or early; we do have civilians in mgmt positions that think little of being late. The way the reuters is touting this makes it look like President Bush was two hours late.