The sabbatical, in various guises, was a critical factor in allowing Ma'a Nonu, Richie McCaw, Carter and Conrad Smith to make it to the 2015 World Cup.
All of them say now the time they spent away from the grind of playing in New Zealand was vital to retaining their physical and mental well-being for as long as they did. It's not exaggerating to say that New Zealand may not have won the 2015 World Cup had it not been for the introduction of sabbaticals.
McCaw would never have made it had he not missed the 2013 Super Rugby campaign and June tests. He was mentally drained after the 2011 World Cup and took time out to see how much he really hated not playing. That he did was the reassurance he needed that he still had that burning desire to be an All Black.
Smith's sabbatical at the end of 2013 was driven by much the same need, to mentally rather than physically refresh. He felt he was close to being indestructible by the time he returned in 2014.
Speaking on the eve of the World Cup, he said: "Physically, I think I could, and even mentally, I could [keep playing test rugby for longer]," he said. "But when you have got a kid at home ... that gnaws away at you more and more and that is the reason why I made my decision [to retire from tests]. Sacrifice is eventually something you no longer want to make. But in terms of my rugby, I reckon I could play another two or three years easily.
"I have played more rugby in the last three or four years than I have any other time, more than when I was 20 and breaking down a lot more. It is funny how it works like that. To me, it is purely personal choice. You can only do the same thing for so long because you become ready for something else."
And now there is a new take on the sabbatical. What happens is that players think they have had enough - their bodies are barely holding up and they feel like they have nothing left to give - so they retire only to realise six months or a year later they were just tired of the routine.
After a break, they feel great, miss the game terribly and are still fit, agile and strong enough to think about returning.
The latest example was former All Blacks lock Ali Williams who, a year after retiring, announced he had signed with Racing 92 in Paris. By May last year, aged 34, he felt he
had endured enough having been a professional since 2001.
He'd won a World Cup and Super Rugby titles and when he switched to Toulon helped them, with a man-of-the-match performance, win the Heineken Cup. There was nothing left for him to achieve and a tired body led to him having a tired mind.
"It's one of those things, when you chuck the game in, you think, 'that's me' and you have no desire to get back playing," Williams said when announcing his comeback. "Then when the body has time to recuperate you think, 'well, there are possibilities I could go again'."
Williams is a direct replacement for another former All Blacks lock, Ross Filipo, whose story is eerily similar. He retired at the end of 2014 after a season with the Chiefs. He was transitioning into coaching, playing a little for his club and hoping to play for Waikato in the ITM Cup when the Chiefs had an injury crisis in 2015.
They rang Filipo and, while he had barely played for his club or trained much, he managed, at 36, to start a Super Rugby game and play out of his skin. He loved it and realised he was keen to play more. And his luck was in, because Racing 92, who knew of Filipo from his three seasons with Bayonne, made him an offer he couldn't refuse.
From being retired, a year later, he was suddenly a key member of a star-studded Racing team that made the Heineken Cup final and then won the Top 14 championship a few weeks ago.
Perhaps the pioneer of this false retirement thing was current Blues coach Tana Umaga. He retired from test football at the end of 2005 and played two more seasons with the Hurricanes and Wellington before taking up a coaching role with Toulon in 2007.
At 35, he was done playing. But when Toulon fell into a spot of bother in 2009, Toulon and Umaga shocked everyone when they announced a new coach was arriving and that the former All Blacks captain was coming out of retirement.
"I think the key is, when I first retired, I'd had enough of just going through trainings and had lost that enjoyment factor," he says. "Then I got that opportunity to come back [and play] when I was overseas and then the same thing to get back into New Zealand, the opportunity that was given to me was to be a player-coach, so I had to play.
"I enjoyed it. A lot of the young players around me gave me a lot of confidence and also they gave me a lot of enthusiasm. It came from them and I shared that and that was the key thing that kept me going. Physically, the older you get, the more professional you become. You know you have to do your warm-ups and warm-downs but when you are younger, you think you can get away without doing it.
"You become better at looking after yourself and it gets you in good habits and you can keep going. If you are enjoying it, you can go for as long as you want. It is when you start to question, 'can I be bothered getting up in the morning and doing my pre-hab?' It just makes your day longer. If you are keen to do that and you can see the benefits, you can play for as long as you like."
Scepticism is healthy but so, too, is acceptance and the sabbatical has probably been the best idea the New Zealand game has come up with in the professional age.
Tana Umaga
Played his last test aged 32 in late 2005 and squeezed out two more seasons with the Hurricanes and Wellington before retiring. Took up a coaching offer with Toulon but, 18 months later, felt like he wanted to play again. Once he proved he was fit and quick enough, he was used as a player-coach, before coming home to a similar role with Counties Manukau in 2010. Did well enough that year to win a Chiefs contract in 2011 aged 38. Probably could have squeezed out one more year but suffered a serious calf injury.
Victor Matfield
The veteran South African lock retired after the 2011 World Cup aged 34, took up a media role and was also a lineout consultant for the Bulls. By the middle of 2013, he knew he wanted to play again, so put himself through an intensive six-month training programme to bulk himself back up to 110kg from 100kg. The Bulls offered him a two-year contract once he was happy he was in the right physical shape and he won back his Springboks place, even standing in as captain during the 2015 World Cup.
Ross Filipo
Played for the Chiefs in 2014 and then decided he'd had enough. He was trying to build a business and coaching career until Chiefs coach Dave Rennie rang him in April 2015. The Chiefs needed a lock at short notice and Filipo knew their systems. He'd played one game
for his club that year but stuck his boots on and looked like he had never been away. Racing Metro offered him a lucrative contract a few weeks later and Filipo was out of retirement and on the plane to France.
