They can't go on forever and will be difficult to replace because the combinations they have formed over time have been incredible.
That's one thing that's improving in the Kiwis' environment. Shaun Johnson and Kieran Foran have now played together for three years and, along with hooker Issac Luke, form a pretty solid spine.
Their experience will be invaluable in leading the side over the next few years and the different skills of all three are exciting. On top of that, guys such as Jesse Bromwich, Kevin Proctor and Tohu Harris have learned in the Melbourne environment what it takes to win games and play for 80 minutes. Add in Adam Blair, who is desperate to play for his country, and it's a good mix.
Johnson is critical in my eyes. We all know he can produce the big play but, as selectors, we're more interested in him doing the right thing at the right time to control a match.
In the past, he could follow up a good run with a poor short kick or ad-lib football that wasn't productive for the side.
From what I've seen, the Kiwis camp still have their feet on the ground. They're saying the right things, like they haven't achieved anything yet, but they also have to believe it.
I still think Australia are favourites for the Four Nations, although England will push them a lot harder this weekend than most are expecting.
The Kiwis still need to improve, especially around their decision making on defence when under pressure.
The way the game is played, momentum can change very quickly off the back of dropped possession and it's then when players are tested mentally.
I think the attack will largely look after itself with the Kiwis, and I liked the way they played attacking football last weekend in the attempt to tire Australia, meaning the onus is on defence.
We can only hope the Kiwis aren't getting ahead of themselves as they prepare to face a physical Samoan side tomorrow because the job is by no means finished yet.