In the early morning of March 15, more than 850 runners will line up at the Redwoods start line to contest 60km, 85km or 100km distances. Of those, 170 will be international runners, including the world's best.
The race is now one of the 10 making up the Ultra-Trail World Tour. It will be broadcast to 120 million people on Eurosport and will go out to millions via corporate sponsors' and athletes' social media. It gets more international media coverage than any other running event in New Zealand, according to Mr Charteris.
With media, athletes and support crews, more than 3000 people are expected in Rotorua for the four-day event. It will bring "easily over $1 million" into the city with the worldwide exposure equivalent to another $1 million, Mr Charteris says.
The speed of growth hasn't surprise him, in fact, quite the opposite.
"I though it would happen quicker ... I was probably too optimistic or too ambitious," he said. "I was impatient others could not see my vision."
The race's success is down to a "genuinely world class" course and Rotorua's infrastructure; the accommodation and tourism options, he said.
Kawerau-raised Mr Charteris used to do triathlons and run but, in his words, he "totally sucked". Then he realised running in the bush and hills wasn't about speed but about moving forward. That, he could do. He began doing ultramarathons.
When he returned in 2008, with the course and vision firmly in mind, he spent eight months organising the first race. The event has grown every year but the biggest boost came when it was included in the World Tour, with numbers doubling from 2013.
Mr Charteris said an independent economic analysis will be carried out this year to work out exactly what the event means for the Rotorua and Kawerau communities.
He's had great support from Rotorua and Kawerau councils, as well as Tourism NZ and Destination Rotorua, but (with a day job at Scion to consider) he can no longer organise it alone.
As race director he heads a team of 12 with about 200 volunteers assisting on the day.
Mr Charteris expects next year's event to reach the 1000 entry limit. It won't get bigger as trails would become too crowded, but he has plans to grow in other ways. "To make sure Rotorua and Kawerau get increased economic benefits from the event ... more major commercial sponsorship ... more media coverage."
He'd also "like to run [his] own race sometime" but for now, there's too much organising to be done.
Destination Rotorua communications manager Jenha White said they were working with Mr Charteris to help him leverage the interest in the event and get those coming to stay longer and enjoy Rotorua's attractions.
"The event is going to be fantastic. Paul has done an amazing job helping it grow and become internationally recognised," she said. "We're really looking forward to the growth."
