I've been entering Nationals since 1993. (And missing 3 or 4 that I hadn't planned on missing!) It's been my experience that people who go to Nationals rearrange "life" for that meet. If we (my team) enter later events on Sunday we usually stay overnight and leave early Monday morning.
However, that being said, I have scratched the last event to catch a plane home (once).
You could e-mail Mark Gill and ask him, he'd be a good resource for actual numbers.
