@pgreehan, I know how you’re feeling about those long times sitting around at staging. The Colorado HS league recently split from NICA and they are implementing some really cool things now that will positively impact the riders. I’m not suggesting you propose that, but more acknowledging that working within the NICA realm can be difficult in terms of getting things changed for the riders.
So in terms of the warm-up, that time frame does seem to be a pretty typical one based on both research and experience. If you do those hard efforts, to prime the system as @PeteD suggested, and then get the timing correct, I would expect the riders to be at an appropriate level of readiness given maybe 15 minutes, but 20-30 minutes is getting on the long side in my opinion.
With the cold temps later in the fall, are the riders wearing extra layers during that time that they can toss immediately before the start? Just thinking of the solid warm-up they had and then having to stand around shivering, I would think some of those benefits would be lost by 20-30 minutes. I’m not sure if the staging area allows for it in terms of space, but even while standing there holding your bike, can the kids jump in place, move their arms, etc. just to keep HR slightly elevated?