Robertson loves pushing himself. He has completed four Ironman events along with many other off-road events.
"One year I cycled to Rotorua and then did the Rotorua Marathon the next day. The hardest event I ever did was the Enduro - riding around Lake Taupo twice - in cyclone-like conditions."
But the Auckland Marathon is the one he always comes back to. He is hoping to achieve the continued enjoyment of participating in the marathon and running with mates.
"It is always good fun people-watching as well."
Robertson said the greatest challenge in keeping his marathon streak alive has been staying injury-free.
"I always make it a goal that if I am not bedridden I will complete the 42km. Anyone can do it. It is just adapting your body to being on your feet for that amount of time."
The Auckland Marathon will be even more special this year for Robertson and his family as his son will be running the kids' marathon for the first time.
"Ryder was born in 2006, 20 hours before the Auckland Marathon, and I made it to the start line with my wife's blessing."
At the other end of the experience scale, Michelle Hardley is also using the Unitec Series to prepare for her second half-marathon.
"It's a good, challenging distance without being overwhelming," she said of the 21.1km race.
Hardley has completed the Auckland half once before in 2hr 13min, and is looking to break the two-hour mark on November 2.
She said her biggest challenge in preparing for the event was getting the flu only two weeks into her training programme.
The 31-year-old accountant shrugged off that early setback and said the Unitec Series, the official build-up series for the event, had added motivation to her training.
The Auckland Marathon is the ultimate inspiration, though, as it is an event that encapsulates what makes the city special.
"I'm a born-and-bred Aucklander, so I feel like it's a must," said Hardley.
She is also excited about the option to be a charity runner as she fundraises for the Cancer Society.
"Not only is it satisfying to be raising money for such a worthy cause, it's also a great motivator."
Unitec Series
Event 4
When: Tomorrow.
Where: Highbrook Business Park, East Tamaki.
Options: 4 laps (28km), 3 laps (21km), 2 laps (14km), 1 lap (7km), kids' race (2km).
Event 5
When: Sunday, October 5.
Where: Barry Curtis Park, Botany.
Options: 4 laps (32km), 3 laps (24km), 2 laps (16km), 1 lap (8km), kids' race (2km).
Online: www.runwalk.co.nz
Auckland Marathon
When: Sunday, November 2.
Where: Auckland.
Options: Marathon (42km), half-marathon (21km), quarter-marathon (10.5km), 5km, kids' race (2km).
Online: www.aucklandmarathon.co.nz