These are truisms of sport and, indeed, life. Getting to the top is easier than staying there. When you reach the summit, the only way is down. Like the changing of the seasons, dynasties come and go. With the exception, apparently, of the All Blacks.
Most World Cup winners have rested on their laurels. New England coach Eddie Jones reckons the Poms are only just shaking off the almighty hangover that set in after their 2003 World Cup triumph.
But after winning the 2011 World Cup the All Blacks went on to greater heights, becoming the first team in the professional era to win all their tests in a calendar year, retaining the Bledisloe Cup and No 1 world ranking and winning back-to-back World Cups.
Surely that was the mountaintop. Surely we're due a rough patch.
Not according to coach Steve Hansen. Despite losing a raft of all-time greats, the All Blacks aren't rebuilding, they're re-establishing. They aim to go to a higher level. They really believe that whiteboard boast about being the most dominant team in the history of the world.
And the public and media expect nothing less. A question of the day on NZ Herald Focus was, "Are the Welsh rugby players ready for our men in black?"
Shouldn't it have been the other way around? The All Blacks haven't played since the World Cup and have only just reassembled. Wales have had the Six Nations tournament and spent weeks in camp. They have a settled, experienced side whereas the All Blacks are missing 11 players from the World Cup final.
Such has been the All Blacks' dominance over the past decade (2007 World Cup aside; speaking of which, who's the ref tomorrow night?) that a generation has grown up knowing nothing else. For 100 years, New Zealanders expected the All Blacks to win; now it's almost taken for granted.
In 2002, I looked into the state of New Zealand rugby under professionalism in my book A Whole New Ball Game. I was trying to show things weren't as black as they were being painted.
One of our leading sportswriters had brought out a book with the incendiary title The Judas Game: The Betrayal of New Zealand Rugby, an indictment of what was widely derided as corporate rugby. The game was supposedly dying at the grassroots and being shunned by the pakeha middle class, the "white flight."
The Wallabies were reigning world champions and had held the Bledisloe Cup since 1998. Australian rugby, already on the up and up, was about to get a turbo-boost from hosting the upcoming World Cup. Because of, depending on your point of view, the NZRU's incompetence or the treachery of the International Rugby Board and Australian Rugby Union, New Zealand had been stripped of its sub-hosting role, an ignominious development that seemed to sum up our decline as a rugby nation and Australia's rise.
The bedding in of professionalism, which came with visible commercial trappings, coincided with the All Blacks having a lean trot. Adding to their portfolio of misinterpretations and premature extrapolations, the doomsters concluded one was a consequence of the other.
The reality was more complex. Former great All Black captain Graham Mourie, who'd become an NZRU board member in the purge that followed the sub-hosting debacle, summarised it thus: "There are four aspects to professional rugby: governance, marketing and finance, competitions, and players and coaches. A huge amount of effort has been put into the first three but we've probably taken our eye off the ball in terms of player development."
What Mourie and our other leading administrators and thinkers on the game understood was that we had to get the governance and structure right and the finances in order to ensure we didn't slip behind our bigger, richer rivals in terms of being able to resource and fund our elite teams. At the same time, we had to maximise our competitive edge " natural talent " by creating great environments headed up by world-class coaches.
To that formula you could add winning the 2011 World Cup, a monkey off the back that liberated the All Blacks to play with even greater freedom and confidence.
So can the All Blacks continue to defy sporting gravity? That it didn't happen by accident is the best reason for believing they just might.