The meetings were over three days Working ten hours a day is reasonable. 3x10 Only Thirty hours to work out a peace agreement on the Korean Peninsula that American presidents have failed to do for decades
3 X 10 hrs - very possible.
Another possibility - 30 hours away from the White House allowed cleaning up of something or other that they found. More bugs, spyware on the computers, phone lines compromised, all kinds of things possible. Maybe even some rogue staff members in the kitchen. Remember, a cook almost scuttled the Red October in the movie.