1. Just saying, at Nationals DD has its own time slot, then there are 6 slots afterward... and people can double up on building events during one slot. (not to be rude or anything)Just saying, there aren't ever 7 time slots at an event so (not to be rude or anything) but I'm pretty sure that's not true... Unless it's a prelim but that doesn't matter because your coach didn't really assign those to you..
2. When I did 6 events in 8th grade, I was later selected for only 4 of them at Regionals, State, and Nationals. Like I said, doing >5 events is an experiment for the coaches to see if a competitor has more than 1 area of expertise, and if he or she does not, then they can pull the plug.
3. Invitationals (prelims) are good indicators of how well the team and other schools' teams will do that season as well as opportunities to get practice tests for future years. If your coach does not assign events at those... ouch.