My first century, I was about ready to die at the 75 mile mark. I was completely wrong on pacing and hydration. I managed to finish but it was NOT pretty. My second century, the following year, I think I did better on pacing and a bit better on hydration, although not enough to compensate for the heat - mid-upper 90's and humid. I don't ever want to feel like that again! But my subsequent centuries, maybe 15 or 16 were much better. Finished tired but nothing like those first two.