Did they know when they started out, the French directors of the New Wave, that they were in it for the long haul? Imagine a young, energetic, passionately cinephilic film-maker coming along today. Given the increasing difficulty of finding finance, generating publicity, staying in fashion, how long would you bet on him or her sustaining a creative career before burning out or caving in to the temptation of the mainstream? Five features? Ten years?

Now take the film-makers who emerged in France in the late-1950s, and who came to be identified as the "Nouvelle Vague". Of the group who made their names as critics in the film journal Cahiers du Cinéma, Claude Chabrol was the first to direct a feature, Le Beau Serge in 1958. That makes the New Wave, as it's commonly accepted – a core of five also comprising Jean-Luc Godard, François Truffaut, Eric Rohmer and Jacques Rivette – 50 years old. In other words, this generation has been making films for nearly half the history of cinema. Who could have predicted that, when, as young polemicists, they were calling for the dethroning of French cinema's tired old patriarchs?

Next month, the group's 88-year-old doyen Eric Rohmer releases his latest film, The Romance of Astrea and Celadon. An eccentric pastoral romance set in an imaginary 5th-century France, the film is atypical of Rohmer's output, which has generally comprised cycles of brittle moral comedies. But Rohmer has veered off course before, most recently in Triple Agent (2004), an austere chamber drama about betrayal, and in The Lady and the Duke (2001), a French Revolution story that made innovative use of CGI, depicting period panoramas as animated engravings.

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As for Chabrol, he has made 55 features in 50 years – usually faithful to his Hitchcock-inspired love of the thriller – and has now embarked on his first collaboration with Gérard Depardieu. Jacques Rivette has gone from intractably challenging experimentation, with films of sprawling duration and logic-scrambling obliqueness, to being a surprisingly approachable classicist. Last year's Balzac adaptation Don't Touch the Axe was a salon-bound romance and magnificently austere vindication of the costume genre.

Other contemporaries sometimes associated with the "New Wave", although not of their film-critic circle, have proved equally durable. Alain Resnais, one of the epoch-defining experimenters of the 1950s and 1960s, is no longer producing his most challenging work, but still commands respect and is making a new film. Then there's Agnès Varda, whose Cleo de 5 à 7 (1962) is the feminist missing piece of the predominantly male New Wave jigsaw. In 2000, Varda embraced the camcorder in her first-person documentary The Gleaners and I, a reaffirmation of the New Wave tenet that the camera could be as personal a tool for expression as a writer's pen.

That leaves two key names. One is François Truffaut, the fiery ideologue who declared revolution in his 1954 polemic "A Certain Tendency of the French Cinema", denouncing the then-dominant generation of conservative French directors and screenwriters. Truffaut died in 1984, his 21 features generally remaining true to a vision of cinema based on emulating the American cinema that he so admired. Who knows where Truffaut would be today? Still making confidently mainstream films, no doubt, although much of his work was less conventional: especially ripe for rediscovery are the melancholy, novelistic Anne and Muriel (1971) and The Green Room (1978), a Henry James-inspired contemplation of death, memory and the image.

Then there's Godard, who, of all the ex-Cahiers group, is reputed as the Promethean grappler with the contradictions of cinema and society. Godard has spent a lifetime crashing into artistic and ideological brick walls of his own making, then brushing himself down and heading off toward fresh crises.

After a torrential spate of invention, beginning with 1960's A Bout de Souffle, he entered an intractably difficult phase inspired by Maoist politics, withdrawing from the limelight to become a video pamphleteer and theoretician. He returned to narrative cinema, reinvigorated, in the 1980s, though he has run aground and revived several times since, and in 2001 staged a dramatic return to public attention with the historically argumentative, visually vibrant In Praise of Love.

Among admirers, Godard now enjoys the status of a philosopher-saint, even if his declarations have been tainted by disturbing strains of anti-Semitic rhetoric. How much more we'll see from Godard is another question: when I interviewed him in 2005, he complained of his inability to make "films" as he used to know them: "It's like being a writer who still knows the letters of the alphabet but suddenly can't form words or sentences."

What is striking is not just these directors' longevity, but also that they have largely remained outsiders, with limited finance. Compare those US film-makers who emerged in the 1960s and 1970s, inspired by the French example: Francis Coppola, Brian De Palma, even George Lucas, who as a student declared of Godard, "When you find someone who's going the same direction as you, you don't feel so alone." (It's doubtful that Godard took such succour from The Phantom Menace).

You might also have expected a "New Wave" to be a quick-burning phenomenon. But while Truffaut may have called for a symbolic slaughter of moribund patriarchs, he wasn't out to kill all parents: he and his peers established a different pantheon of precursors, most famously Hollywood directors such as Hitchcock, Hawks, Ford and Fritz Lang. There were idols closer to home, too: Renoir, Bresson, Jean-Pierre Melville, Roberto Rossellini. These elders were themselves notable for sustaining long careers: their teaching was that, whatever challenges the film industry or world history threw at you, you had to keep filming. The New Wave generation similarly contrived to endure, to make features even when there seemed to be no money to make them with or, for that matter, no stories to tell. Rivette has made a career of pulling no-budget projects from the jaws of disaster: both Don't Touch the Axe and his hall-of-mirrors fantasia Céline and Julie Go Boating (1974) emerged overnight from the collapse of other projects.

Remarkably, these directors' collective achievement has never been repeated. French cinema is forever in search of an enduring "New New Wave", but none has delivered. The self-important stylists of the early-1980s, Jean-Jacques Beineix, Luc Besson, Leos Carax, ran out of steam. That 1990s firebrand Mathieu Kassovitz (La Haine) was last seen directing a Vin Diesel sci-fi vehicle. Of today's enfants terribles, who'll last the course? Gaspar Noé? Too cranky, too slow. Christophe Honoré, whose recent films (Dans Paris, Love Songs) are a hymn to the early New Wave? We'll see.

No doubt what sustained Truffaut's peers was that they grew up on film as a religion, to the exclusion of much else. For subsequent generations, film has been one cultural attraction among many, so the stakes have never again been as high: you can make films or not, but life goes on. Compare Godard in 1962: "Shooting and not shooting, for me, are two different lives. Filming should be a part of life."

The New Wave directors stayed true to that imperative and avoided becoming relics. Their later work is generally as fascinating as the early breakthroughs: it's not a question of choosing between Godard's Alphaville (1965) and Histoire(s) du Cinéma (1990s), Rohmer's Claire's Knee (1970) and Triple Agent (2004). It's all part of the same long-term adventure, an achievement of marathon runners rather than sprinters. And it's not certain that the baton has yet truly been handed on.

'The Romance of Astrea and Celadon' is released on 12 September. Claude Chabrol's 'A Girl Cut In Two' is released next year

Riding the wave: Who says old dogs can't pull off new tricks?

Jean-Luc Godard

After his Histoire(s) du Cinéma video essay of the 1990s, Godard returned to fiction with 2001's Eloge de l'Amour, a diptych about the legacy of the Second World War. His 2006 installation at Paris's Pompidou Centre baffled many, but drew the crowds

Claude Chabrol

The most traditional of the New Wave directors, Chabrol continues to produce new variations on his Hitchcockian thriller template. His latest film A Girl Cut In Two is about an ingenue caught between a roué novelist and a volatile rich boy

Eric Rohmer

For years, it seemed you knew what you were getting with Rohmer. Recently, he's perplexed fans with ventures into French history, espionage and now pastoral idyll, in The Romance of Astrea and Celadon. His 2001 The Lady and the Duke saw him experiment with CGI to dazzling effect

Jacques Rivette

Last year's Balzac adaptation Don't Touch the Axe was arguably one of France's finest ever costume dramas. In 2006, fans swooned at long-overdue screenings of Rivette's little-seen 121/2-hour soap opera-cum-conspiracy thriller epic, Out 1 (1971)