I have never done a solo century nor have I even considered it. I've ridden many (hundreds) but never alone. My first was in 1988. I had been riding the bike path on a heavy clunker for about a year and bought a nicer bike and started going out on the road with a guy I met at the path. He wanted to do a century so we trained some, did a few 50s and one 75 before the big day. It was organized but I don't remember much support. It was fairly flat with some crappy roads and I had some respiratory crud. I didn't think I could finish and did a lot of whining and sniveling. I wish I had trained more, maybe a few more 65-75 mile rides, and I shouldn't have done it sick. My next one was 4 months later and I had a much better time even though the ride was a lot harder. I never go for speed and my centuries take between 6.5-8 hours, as much as 11. In the early 90s I did one every weekend at least for 3 years. Like the man said "90% of this game is 1/2 mental".