411A,
You're usually best ignored so with that in mind this is for the benefit of open-minded, non AA ax-grinders....
DIA is a huge airport. Taxy time varies but safe to say, given the reduced visiblity at the time, it could take this crew at least the ten minutes it took me when I was there a week ago, on a VFR day.
At the gate, a shutdown checklist takes a few minutes whilst the passengers begin to deplane. It can take up to ten minutes for them all to get off.
At this point in time, assuming this crew and airplane continue to another destination, the CA leaves the airplane to get the paperwork, check WX etc and the FO "sets up" the flight deck per before starting engine checklist. This may account for another five or six minutes.
Finally the FO then leaves the flightdeck to check the outside of the airplane, known as the "walk around".
I was not there but this timeline is somewhat typical for a through flight.
DD