If I was riding an upright bike, I'd have to increase my mileage in steps, until my butt could handle it. With my recumbent, I just go out a few times. A couple of 30 mile rides, maybe a metric century, then I'm ready for the full. I did Horsey Hundred one year with about 100 miles' training leading up to it. Don't expect to be able to push the pace unless you've got a lot of miles under your belt, though; with less than 500 miles in, you'll be pretty much in survival mode the whole way.

The first century I ever did was on a 4-day tour that averaged 82 miles per day. Training involved a 35-miler and a few shorter rides. That was BB (Before Bents) and I was SOOOOORE for days afterwards!