Yeah, you can do this! If you have managed to get up to 80, than 100 should be no problem. Yesterday, I rode my 3rd century of this season. I did 1 in May, 1 in June, and then yesterday...and I plan on doing 1 more in September. Although, these were all self-supported centuries...not organized events with designated rest stops and SAG support. I actually didn't set out to do a century yesterday...but when I hit 90, I figured..."what's 10 more miles, right?" Maybe another 40-45 minutes...I can do that. So I did. Like the other poster said...don't think of it as 100 miles. Break it down into smaller segments, that way it seems more manageable.