He spent a couple of years in England from 2011 and didn't really enjoy the experience. He likes home, which in his case is Matangi in the Waikato, by way of his parents' property at Outram near Dunedin, where he was born and raised.
"I like living in New Zealand. It's home and that's where I want to be," Johnstone said.
"It makes it a bit harder for team selection but hopefully that result in Adelaide will have impressed the selectors."
He could have added that as New Zealand's best performer at last year's Rio Olympics, where he finished sixth on his outstanding 13-year-old Balmoral Sensation, the horse on which he won in Adelaide, Johnstone is making a solid case for next year's World Equestrian Games team to compete in Mill Spring, North Carolina in September.
Johnstone's thoughts are firmly locked on what Balmoral, his only true four star horse, is capable of. Travel takes plenty out of horses and while last year worked out well for the combination, Johnstone is reluctant to push the horse too hard.
"You can't do everything with one horse," he said. "The last time I went to Europe, I did Adelaide two years ago, then Badminton [finishing fifth], then the Rio Olympics.
"It all went really well but it took a lot out of the horse and I think he would be better at the worlds if he had a lighter 2018 in the build-up."
He is prioritising the World Games and Tokyo Olympics in 2020. He acknowledged there will be a European component to his programme next year but is still working the best way through the situation.
"I think I can prepare just as well here as in Europe. Unfortunately not everyone else shares that opinion."
And Johnstone is also proving himself a burgeoning showjumper. That beckons further down the line and competing at the highest level in that discipline has some appeal.
It would be a stretch to say he could follow in the great Todd's footsteps and compete at an Olympics — in Todd's case, 1992 in Barcelona — in both the eventing and jumping disciplines but you wouldn't rule it out.
"I'm really enjoying it and I've got a couple of nice horses, who are quietly moving up the ranks and jumping at the top level in New Zealand."
Johnstone cited 10-year-old Quainton Labyrinth as one with a particularly bright future.
That's for later, though. For now, Johnstone is in a good space, in good form and eyeing the future in a positive light.
He was jumping at the Quintana international in Auckland this week, and is off to Rotorua this weekend for more eventing.
"It's all go, and everything's going pretty well."
New Zealand's four star classic victories
Burghley 13
Mark Todd 5 (Wilton Fair 1987, Face The Music 1990, Welton Greylag 1991, Broadcast News 1997, Diamond Hall Red 1999).
Andrew Nicholson 5 (Buckley Province 1995, Mr Smiffy 2000, Avebury 2012, 2013, 2014).
Blyth Tait 2 (Chesterfield 1998, Ready Teddy 2001).
Caroline Powell 1 (Lenamore 2010).
Badminton 6
Todd 4 (Southern Comfort 1980, Horton Point 1994, Bertie Blunt 1996, NZB Land and Vision 2011).
Jock Paget 1 (Clifton Promise 2013)
Nicholson 1 (Nereo 2017).
Kentucky 3
Nick Larkin 1 (Red, 1998).
Tait 1 (Welton Envoy 2000).
Nicholson 1 (Quimbo 2013).
Adelaide 3
Larkin 1 (Red, 1997**)
Matthew Grayling 1 (Revo, 2001)
Clarke Johnstone 1 (Balmoral Sensation 2017).
Luhmuhlen, Germany 2
Nicholson 1 (Mr Cruise Control 2013)
Tim Price 1 (Wesko 2014).
Pau, France 1
Nicholson (Nereo, 2012).
Note: ** denotes won when event was officially listed a three star.