The 52-year-old, who now divides his time between Sydney and Queenstown, will compete in the Western Cape's Absa Cape Epic eight-day mountain bike stage race in March, with team-mate Ross Weston (48), of Wellington.
Each year just 680 teams are allowed to enter the race, dubbed "hors categorie" by the Union Cycliste Internationale, a term used in bike races to designate a climb that is "beyond categorisation".
Over the eight days, the pair will traverse 658km, with 15,755m of climbing, and must stay within two minutes of each other at all times.
"That creates a bit of angst, actually, because you can wake up one day and one of you can feel really good and the other one might feel shattered _ you've just got to ride to each other and communicate heaps," Mr Stephens said.
"We laugh a lot, but every now and again it gets a bit dark, so humour helps, but you've got to be really conscious of your partner all the time."
It will be the second attempt for the pair to compete in the Cape Epic, now in its 19th year, having won an entry by lottery ahead of the 2020 edition, which was cancelled the day before the race was to start, due to Covid.
"This is very much unfinished business."
Mr Stephens, formerly a road cyclist, only started mountain biking about six or seven years ago, but quickly became hooked.
He first met Mr Weston on a mountain bike weekend, after which the pair competed in three Pioneer mountain bike races in New Zealand, in 2017, 2018 and 2019.
While Covid had disrupted other planned races _ and training _ they competed in the five-day Swiss Epic this year, another hors categorie race, after which Mr Stephens said he was "knackered".
"There's a lot of climbing, and that's the killer.
"You can just spend hours climbing up those hills.
"The downhill's fun, but you've got to concentrate ... the climbing's the thing that completely just blows your gasket."
The pair would also have to be mindful of an invisible threat, gastroenteritis, something the race was renowned for.
"The water's different and the different sorts of food, they play havoc with you ... we're thinking about buying water, or taking those purifier tablets, but then we're a couple of lads from New Zealand, we should be pretty safe, I reckon."
Aside from other more obvious threats, like rocks, they were also conscious of the heat _ though given it was likely to be similar to Central Otago summer temperatures, Mr Stephens said his summer training was helping with conditioning.
"We've got a place at Speargrass [Flat], and I just spend days climbing ... I went up Mount Dewar yesterday, we just do all the trails around Central Otago, they're fantastic.
"We've had really good weather here the past few weeks, everything's really dry and we've had stinking hot weather the last few days, I think that's exactly what it's going to be like over there."
Ahead of the race, which runs from March 19 to 26, Mr Stephens said he was "excited and nervous", but also had one other mission before they fly out.
"I think I'm fat, so I've got to lose some weight," he said, laughing.
