Originally Posted by Homeyba

Don't worry too much about your speed right now. It'll come. What's more important is to be monitoring it and pay attention to what your body is doing. Learn where you "red zone" is and where your comfort zone is. Riding distances is all about knowing your body and learning when you need to back off and when you can hammer it.

I'll tell you about a friend of mine. He wanted to try a little experiment. He was going to do a 780 mile in 90hr event called Paris-Brest-Paris without getting on his bike at all for the year prior to the event except to ride the four qualifying events. He was able to do all the qualifiers and PBP. He was sore but he did it because he was in tune with his body and how it worked. He never pushed his body too far and was able to pace himself. The human body is an incredible endurance machine if you let it do what it can do! A hundred miles seems like a lot but if you continue training like you are and don't push yourself too hard on the century you're going to finish that hundred miles and think "wow, I could do another hundred!"