Well 4 years makes a world of difference. When I rode my last 600km, it was a qualifying ride for the 2007 PBP, and I did the ride with the New Jersey Randonneurs bike club and most of the ride was located in South New Jersey and was ridiculously flat compared to the terrain between Paris and Brest. Even with it's lack of challenging climbs, I limped across the finish line and it took a couple days of recovery before I was not in pain walking on stairs.
This year I have really made a concerted effort in training- not only with my riding but eating well and stretching. After riding 370 miles I felt great, I could have ridden many more miles. That is such an amazing feeling. As a matter of fact, even after the ride over the weekend, 3 days later, I went for a run. I am now convinced that I will succeed in France and will not be too wiped out after doing it.
I'm contemplating writing a detailed ride report, with some of the challenges in doing such distances, and commonly asked questions people ask me- what does one think about while riding a bike for 30+ hours. We'll see.