Two years ago I did the 80 mile route on the Knox County Bicycle Challenge and it just about killed me (4500 feet of climbing, most of it in the first 50 miles). This year I did the same route and it was enough. For '09 I want to do the full century route - which is more than "just 20 miles more," since the 80 mile route flattens out after the 50 mile split while the 100 continues in the hills. That ride is in September so barring major problems I should have all summer to train.