It's worth remembering the 31-year-old, who won gold and bronze at the last two Games, is in some of the sharpest form of his career as he prepares for the 5000m-1500m double at Hampden Park.
In May he set a personal best time for the 5000m. Then he became the second New Zealander after the great John Walker to break 3min 50s for the mile.
A week later, he shaved 0.58s off Walker's 31-year-old 3000m record, with a 7:36.91. And several days ago he set a New Zealand record 3:29.91 over 1500m, 0.44s better than the previous record, at the Monaco Diamond League meet.
Has he surprised himself?
"Yes and no. Over the last four years there have been hints of this happening. I just haven't been able to sustain it. It's just about getting the timing right."
He's been working on endurance and not worrying about straight speed, and reckons it's working.
The Monaco time, in a race in which he finished seventh, was immensely encouraging. He was "probably the happiest seventh placegetter in the history of our sport".
After the London Olympics, Willis started a masters in marketing and fancied following a move into the corporate world.
"Then I had the birth of my son and I thought, 'this is a fantastic job', to be able to spend as much time with my family and make a living out of it.
"So I want to hang onto this as much as I can. I'm working only a couple of hours a day but I'm able to support my family. I'm going to try to do this as long as I can."
That means not only Rio in 2016 but also the 2018 Gold Coast Commonwealth Games.
His old mates from Lower Hutt have been badgering. They want to see him there, even if he's running the marathon by then, he quipped.
For now, there's the 5000m tomorrow morning (NZT), a field trimmed by the high-profile withdrawal of double Olympic champion Mo Farah, and the 1500m final next Sunday morning (NZT). And then it's back to changing nappies.