My guess and feel is that 15min. would be the max = But in the end, Fenrir should decide.
In the past we've had some startup / spawning issues, and well, time flies when you try and fix them. And next, before you know it... we are running late. Mostly, when all goes well, we finish flying around 23:30 CET (which is my time zone) - then a of debrief ... before I know it, it's tomorrow already! For sure, I can postpone bed time, but I know there's also people going to work after the mission ends ... lol.