It appears the best way to increase the total mileage for a ride is to break the ride into segments and only concentrate on each segment.

That approach does sound reasonable. I have been thinking of how totally exhausted I have been at the end of each century and that I could not have gone another mile.

I have worked hard to hydrate correctly and eat correctly on the centuries and have been surprised at how exhausted I have been. That exhaustion in spite of my work on my hydration and food intake is the reason I decided to ask about the mental difference because I felt I had prepared very well for the centuries.

The 200K I want to attempt is an official brevet. I knew the time allowed was over 12 hours, but I could not remember the exact time. I have not stayed on a bike for more than 7 hours, so that will be a new experience and that brings up another question, if I may. I have two bikes, a road bike that I have ridden on my centuries and a newly acquired Surly LHT. Which bike should I use for the 200K?