"Sometimes I can't believe that I have done 11 of these events but I guess it's a cool thing to look back on."
She has her sights set on the goal of completing 20 Taupo Cycle Challenges and is now part of the bronze cadence club, which means completion of 10 solo events. If she gets to complete 20 finishes, then she'll be in the gold cadence club.
"I want to do 20, why not? After that we'll see what happens but, yeah, I'll try to get to 20 first. That is the main goal and I'd love to get there."
There is no easy way to ride 160km. Smart training is the key.
"It's 100 miles so, yeah, you do notice it. It's a good distance and by the end you are well and truly knackered."
But it is the most satisfying feeling crossing that finish line and the atmosphere there is amazing.
She admitted it was getting harder to fit in the training required.
"Nowadays I am training about 300km per week. It is very hard to fit in the training sometimes but I love it so I always make it happen. I don't work a full-time job, which helps, and I get plenty of training riding and helping out with my local club, Taupo Cycling Club, and also with mountain bike guiding, so that helps get the miles up."
Duncan said her hometown of Taupo was a fantastic place to ride.
"It is not hard to be inspired down here. Everywhere you ride there are stunning views of the lake and the mountain."
She is also invested in helping riders of all abilities. Duncan is one of many members of the Taupo Cycling Club who put on a training course for the Lake Taupo Cycle Challenge entrants every year before the event to help rookies get familiar with some of the skills required to ride it well.
They teach people skills such as riding in a pack and pacing your ride and cornering, all of which are really important in the Cycle Challenge.
"We take them through the first 20km of the course which is always a bit of an eye-opener."
Even though she is in the 45-54 year age category, Duncan is not slowing down. She is again aiming for a very respectable sub-five hour time.
"The past three or four years I have managed that but it really does depend on the weather. We had a great day in 2010 and that made a big difference. Anything is possible."
The best advice, she says, is to practice hill-riding and to get used to riding in a bunch.
What advice do you offer to newcomers to the cycle challenge?
Sheryl Duncan, 47, 11 Taupo Cycle Challenges: I would offer two pieces of advice. Get some practice on the hills. The first part of the event is tough and you need to be ready for that. Secondly, 10,000 people on bikes is a lot of people and can be chaos. Make sure you have done a bit of riding in bunches and get used to riding with a lot of people around you. If you are doing the solo ride then the start and first 20km or so is pretty crowded. The Taupo Cycle challenge is an awesome event and I would recommend it to weekend warriors.