Steamy warmth envelopes Sam Alexander on the outskirts of Canberra as he tightens a girth strap and steels himself for a wet spongy saddle.

On average, only three people a year finish the 5330-kilometre journey he's on, from one end of eastern Australia to the other.

This is the 24-year-old medical student's first break from text books since high school. Three weeks before getting into the saddle he broke in two bay geldings, Ranger and Laddie who are on the ride with his chestnut mare Marda.

Moonlit trails and snowy peaks have led them through lean times in the high country. So they're on a break near Canberra where the horses are regaining weight in a lush paddock at Hall.

Mr Alexander says managing them and understanding their psychology are his biggest challenge.

In brumby country he discovered Marda was in season and ready to push her luck with his portable electric fencing.

''Just as I was making my way into Canberra … and stuck in a freak snow storm, the electric charger died.''

In -10 degrees and his pyjamas, picturing between 150 to 200 brumbies he'd seen lately, he'd got up and out of his tent seven times in the night to retrieve the horses.

The trail's voluntary chairman, Mick Jacomas, said five people were currently on the course, which runs from Healesville, Victoria, to Cooktown in far north Queensland.

Many people tackle the trail on bikes, horses or foot in sections at a time. They include Canberra Airport owner Terry Snow.

One man had been on and off it for four years, some went for weekends at a time, while another couple, Craig and Shirley, of Queensland, had just finished it after five years.

Mr Alexander met Craig and Shirley three days after he had started.

''They gave me heaps of hints and small batons which I will give back to them when I make Queensland.''

On the trail, he's up at daybreak and spends two hours packing up a fold-out solar panel which power his mobile phone, satellite phone and mini computer, tent, mattress, sleeping bag, three medical text books, novels in the Lord of the Rings trilogy, dehydrated meat and a little grain to keep protein up to the horses.

''The last few nights, it's been so cold and we've been so high up the last thing to pack up will be my tent because it is so frozen. You can bend it like a bit of cardboard, so you need the sun to let it thaw out a little.''

He's lost the horses twice, once while unpacking them, and spent hours finding them. He rode up and down Mount Terrible, Victoria, finishing late at night in mist so thick he had to switch off his headlight because of the blinding reflection. A little path appeared, as did its name: Moonlight Spur. ''That's pretty much the way I was navigating. All by moonlight.''