velojym

Before my first century, an Akie 100 (Arkansas), just for my own mental comfort, I decided to bust a hundred before the event. We had a 60+ mile club ride on a Saturday, and after that, I rolled down to the river trail to lap out the rest. After clearing 100, I approached the event ride with a lot more confidence.
As mentioned before, if you're training rides are up to more than half of the event ride, you'll be fine.

One other thing... many will suggest keeping a steady pace through the ride, but there are exceptions. When I rode in the Hotter'n'Hell Hundred, I knew it was gonna be a scorcher. So, I pushed a bit harder earlier in the morning (unwittingly dragging a pretty hefty paceline) over the first quarter of the ride or so. As the day heated up, I moderated my pace and played it safe, staying well hydrated and fueled for the rest of it. Don't play around with that heat. They had helicopters waiting around, just in case.