For Allan it will be a case of expecting the unexpected, after finishing runner-up in New Zealand's premier multisport race the past two years. A world-class field will still await him on Kumara Beach tomorrow. But for Allan reputations account for little on race day.
He took the race by storm two years ago when he went head-to-head with favourite Gordon Walker (Auckland). Walker edged away in the closing stages to win a third title. And last year, despite a conservative start, Allan impressed over the second half of the course to break away from Carl Bevins (Christchurch), another of this year's favourites, and finish second behind Richard Ussher (Nelson).
Ussher, 35, is returning this year, chasing a fifth title, and Allan knows he will be hard to stop, but knows also, victory will be all the more noteworthy with a scalp such as Ussher's.
Ussher won his first Longest Day title in 2005 and went back-to-back in 2006. A full-on frontal attack, right from the start, from Walker denied Ussher the hat trick on 2007.
Walker attacked the initial 55km cycle section from Kumara to Aickens, a tactic many would consider suicidal in the 243km race. But it played on Ussher's mind over the 33km alpine run. The likes of Allan could employ a tactic like that. he opted last year to compete at his own pace over the first half of the course.
"I feel I'm better prepared than I've ever been," Allan said.
"But as in a lot of these races, it can come down to how you feel on the day."
But any risk may be just that, for, as well as the world class of Ussher to overcome, there is Bevins, who will have also learnt a few tricks from his experience in the chase group with Allan last year.
There is also Braden Currie, the younger brother of Methven school teacher Glen Currie, who finished third behind Allan and Ussher last year.
Currie will take into the race the advantage of training with Allan over the past two weeks in Wanaka.
Among other favourites is last year's two-day champion James Coubrough (Wellington), and world shearing champion Paul Avery (Stratford), who finished third in the two-day section last year.
Prominent internationals include Andy Blow (Britain), and Simon Niemi (Sweden).
An added incentive for Ussher will be his wife Elina, the 2010 champion and a runner-up last year. Should she win the women's section and he the men's, they will become the husband and wife to win on the same day. Keith Murray (1994) and Andrea Murray (1997) are the other successful husband and wife combination.
But Elina Ussher will have to overcome tough challenges from Fleur Pawsey (Christchurch), Rachel Cashin (Taumarunui) and internationals Sia Swendsen (Sweden) and Brazian champion Camila Nicolau.
The two-day race starts today at 7am and the Longest Day tomorrow morning at 6am.