Ive long believed that the very fastest riders have a tendency to favour 400km DIYs over calendar events as a quick rider can batter round in daylight in a way that many others just cant.
Pretty much any audax event (but especially those 400k upwards) will force organisers to make tricky decisions and trade offs.
Most will tend to try and find a sweet spot for the majority but when faced with an issue where its full value riders v. fast riders (eg determining a start time to dovetail with ferry crossings) the former will be given priority for obvious reasons.
Thats why organising or helping at an event is such a good idea, appreciating audax events from a slightly different perspective definitely improves ones audaxability 
as it will provide a more ready answer to the question “Why did the organiser do *that*?” that Im sure we all experience from time to time when riding an event.
On the 400 I ran there was an 11 hour spread between the first and last riders back. It was a long slog. To make it harder it was figure-of-8 and the last rider to leave went out the door about 2am and the first back was in at 4. There wasn't a lot of sleep going on amongst the 3 of us working in the hall.
I think X rated rides cater much better for faster riders. I used to enjoy the Asparagus and Strawberries as I would be back for breakfast and could catch the first train back to town. These days I book a hotel near the finish and can be back in bed by 2am. I then pootle down to the finish on the morning, hand my card in, and have breakfast.
