Jc,
Good question about APU inop at night.
The FOM says boarding or deplaning passengers is not normally done with an engine running. This implies that exceptions can be made.
I would say it would be okay to deplane the passengers with the No. 2 running then shut it down after the last passenger got off. After all, there's still a chance that the APU will start after an hour.
Darkness engenders a whole new set of risks. Ground staff might still be sleepy (early morning) or already tired (in the evening.) Keeping an engine running during the ground stop really increases the risk of very big FOD.
Besides, you can use the one hour interval to ask the taxi drivers in the parking lot where the best party places are.
This really should be on a different thread because it has nothing to do with management.