Clermont are a great team, of that there is no doubt, but are the good times coming to an end? © Getty Images

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Endless television replays, interminable matches, overblown pre-game entertainment - in some ways rugby has already taken on many of the less desirable traits of US sport.

However there is one concept from across the pond which we are going to become a lot more familiar with over the next few years. Ask any American sports fan about the 'Championship Window' and they will know exactly what you are talking about - the period of time a team has to win a title before they cease to be a contender and have to rebuild.

Whereas European sports tend to see the same clubs dominate year after year, equality is king in the States, making it difficult for teams to compete at the highest level for extended periods.

The dread for the sports fan is seeing their championship window slam shut. This weekend the New England Patriots will take on the Denver Broncos for a place in the Super Bowl knowing that both their windows are closing with 36-year-old Tom Brady and 37-year-old Peyton Manning as their quarter-backs.

In basketball the Miami Heat, winner of the last two NBA titles, knows that their window will slam shut if they are not able to re-sign free agent Lebron James at the end of the season.

So how does this concept apply to rugby - a sport where we are seeing the rich get richer and everyone else get left behind?

Well the championship window is not just based on great players, after all Mourad Boudjellal has proved at Toulon that you can always get more of those. It's also centres on coaches installing their philosophies and moulding their team.

In the week they booked a place in the Heineken Cup quarter-finals by winning away at Harlequins, while sitting pretty at the top of the Top 14, it seems odd to talk about Clermont Auvergne's championship window. But dig a little deeper and there is a danger that this might be their last chance before they need to rebuild and go from contenders to outsiders.

The most obvious change for Clermont at the end of this season will come with the departure of Vern Cotter, the New Zealander who has been in charge since 2006 and led the club to their first ever Bouclier de Brennus in 2010 after ten lost finals.

A hard-nosed pragmatist, Cotter transformed the club by instilling a discipline in terms of both training and nutrition. That's all too rare in France where international players can still be spotted sneaking off for a fag after a game, or where a croissant is an acceptable post-training snack.

Cotter will be off to Scotland next year, leaving current backs coach Franck Azema and Leinster forwards coach Jono Gibbes to take the reins.

With the unwavering support of tyre giant Michelin, some of the most passionate home support in Europe and a squad packed with talent, the transition looks like it should be easy. But there is a sense that Cotter has picked his moment wisely. Clermont are formidable but the spine of their team is getting on in years, and replacing them will not be easy.

Clermont's Sitiveni Sivivatu is off at the end of the season © Getty Images

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Aurelien Rougerie, the emblematic captain who was born ten minutes drive from Stade Marcel Michelin, is edging closer to retirement and while Jonathan Davies is arguably the standout outside centre in Europe, it will take more than that to replace the man who has led the club for eight years and been in the first team for 14.

Rougerie will still be there next season but the same will not be true of Lee Byrne and Sitiveni Sivivatu. Jean-Marcellin Buttin looked a very capable replacement for the Welshman at the weekend but it will be tougher for new man Zac Guildford to fill the boots of the former All Black. Even if his form has dipped a little in recent weeks, Sivivatu has been the best player in the Heineken Cup this season, beating defenders for fun and creating mismatches all over the park.

There is also the fly-half question, with Brock James the wrong side of 30 and potential replacements Camille Lopez and François Trinh-Duc choosing to move to Perpignan and stay at Montpellier respectively. In the pack the need for fresh blood is even more urgent.

There isn't a more rugged second row in Europe than Jamie Cudmore and Nathan Hines, but both have turned 35 and age will catch up with them sooner rather than later. The same is true of Julien Bonnaire, arguably the most successful player from the great Bourgoin production line.

The arrival of Sébastien Vahaamahina will help bring down the average of the pack, and could prove inspired, while the likes of Morgan Parra, Wesley Fofana and Thomas Domingo will help the next generation settle in. Add to that fortress Michelin, which has not been breached in four years, and Clermont are not about to disappear off the map.

But the window for this generation might just be closing, and Cotter, Rougerie and co would be well-advised to add to that solitary Top 14 title and vanquish their Heineken Cup demons before it shuts altogether.