I rode in the Bike MS in New Bern, NC this past weekend. What a great event! Over 2400 cyclists. I just started riding seriously in March. Longest training ride was 50 miles, but in hilly terrain, and the century was flat. My GPS said 98.96, but that's close enough for me. The last 10 miles were tough. My knees were hurting in the front. I raised the saddle 3/16" and did 50 more on Sunday.
If you are into charity rides, this one is superbly done.