At home in the leisure of my garage including wipes downs and careful inspection of rim, tire, etc.: 20min

On the side of the road solo: 5min

On the side of the road with three other cyclists trying to help and give advise and two pressuring everyone to hurry up: 10min

Anyway, for me sometimes the most time consuming part is the inspection of the tube and tire to find exactly the cause of the flat. 3 extra minutes there can be 15 saved down the road.

I've done 2min roadside fixes on the rear wheel when I see the culprit on the outside of the tire, pull out a bit of the tube, put a patch on, stuff it back in, pump up and go. No need to even take off the wheel.

Al