The Briton is in Kona, Hawaii ahead of his first Ironman World Championship on Saturday (12 October).
Since retaining his title at Rio 2016, Brownlee has competed largely in Ironman 70.3 events - also known as half Ironmans - with a view to eventually stepping up to the full Ironman distance.
The Yorkshireman has refused to commit to defending his Olympic crown at Tokyo 2020, but this week told The Sun, "Once I get Kona out of the way, and see how that goes, then I will start thinking about next year. Perhaps even by the time I’ve crossed the line in Kona or maybe a few days after that, I will probably know what I am doing for 2020.
“Whatever happens, though, Tokyo is 100 percent my final Olympic triathlon… though I probably said that after Rio in 2016!"
Change of plan
At the start of June, Brownlee's path to Tokyo looked fairly routine.
He appeared to be back to his best after a succession of injuries with the World Triathlon Series event in Leeds representing a great opportunity to clinch a win which would put him on course for next year's Games.
But things did not go according to the script.
Despite plenty of local support, Brownlee trailed home in 44th place after an uncharacteristically poor running leg and told the BBC he "might retire" before later saying he would "sleep on it".
Then came a dramatic change of tack with the 31-year-old opting to make his full Ironman debut in Cork just two weeks later.
With the swimming leg cancelled due to poor weather, Brownlee took victory in the bike-run duathlon to secure qualification for the Ironman World Championships.
Before that Hawaii engagement, he had the Ironman 70.3 World Championship in Nice, France in early September.
For the second consecutive year, the double Olympic champion had to settle for silver with Norway's Gustav Iden finishing almost three minutes in front.
Heading for Hawaii
Brownlee's first trip to Kona for the Ironman World Championship is something he has been looking forward to for "over 20 years".
On his YouTube video series, 'From Yorkshire to Kona with Alistair Brownlee', he said, "Everyone has told me, 'You've got to go, you've got to experience it, you've got to go and watch before you compete.'
"I didn't really want to go all that way just to spectate so I think going to race for the first time is fantastic. But I've probably got to be a bit realistic in terms of learning about how the race works, how to prepare for it, what racing in a championship Ironman race is actually like compared to what I've done so far.
"I think there is quite a lot of things that will be new to me and I'm seeing it as a big learning experience but, that said, I'm hoping to still be pretty competitive."
While completing his preparations in Arizona, he told The Sun, "I keep being told that no-one does really well in their first attempt. It seems like a big ask. But when I get on the course, I will give it everything I have.
“One of the things which is welcome about this is being the relative underdog and not having too much expected of me going into the race. I like the fact it’s new to me."
He added, "The pain will be different. It’s not Olympic-distance racing when you are really pushing your body to the ends of its abilities in terms of what you are doing in that time.
"It’s a case of, ‘This is uncomfortable and I have got hours to go.' You do think more than once – why am I doing this? But I love racing. I love being competitive and love triathlon."
Brownlee has already given notice that he will be among the contenders by winning Sunday's Ironman Training Swim.
Brownlee is clearly taking this competition very seriously indeed, despite not being among the favourites.
“I hope to have another 5-7 years of the long-distance racing in me. And if I can do well in Kona, then it would rank very highly in my career. A close third after the two Olympic gold medals." - Alistair Brownlee speaking to The Sun