Several ways to do this. However I need a clarification. Do you want 30 mins to an hour of time to actually pass by or do you want to jump forward in time? You can use skiptime to jump forward. If you want time to pass before the other units go to the scene, you can use the Min/Max/Mid time control variables in the waypoint before they go to the scene. Time is input in seconds. You could put 1800 in min, 3600 in max, and 2700 in mid for example. This would make them show up somewhere between 30 mins and a hour after mission starts with a tendency to come around 45 mins into mis.