The average running times of films has increased: welcome to the era of the epic

The average running times of films has increased over the decades: welcome to the era of the epic.

If 162 minutes wasn't enough, stay tuned for the Avatar Extended Collector's Edition.

In one of the crucial scenes in James Cameron's Avatar, Sam Worthington's tortured hero Jake utters the warning "you have to leave or you're going to die". It might have been a warning to the inhabitants of Pandora, but to anyone who was struggling with the length of Avatar, toying with a quick exit from the cinema, it felt remarkably apt.

The film might have been the most expensive ever made. The 3D CGI might have looked sumptuous. And yes, it's the most successful movie of all time. But that didn't mean, surely, that it had to be an excruciating 162 minutes long.

Of course not. It had to be longer. That's the staggering conclusion James Cameron has reached not once, but twice, in a year. The Special Edition, released in August, added another nine minutes - taking us up to 171 minutes. But that still wasn't enough. In November, we'll be treated to the not very snappily titled Avatar Extended Collector's Edition, which has a further seven minutes, plus 45 minutes of deleted scenes. Cameron called the DVD release "everything the fans could possibly want". We'll be the judge of that, thanks.

Cameron, of course, has form for this kind of epic film-making. Titanic is a proper classic, but a frankly ridiculous 194 minutes long. That's more than three hours to tell us what we already knew - that a big ship hit an iceberg and sunk. It's not all Cameron's fault - films are definitely getting longer. All of the movies in Peter Jackson's Lord Of The Rings trilogy clocked in around the three-hour mark - the extended version of The Two Towers a staggering 223 minutes. Once you've seen the trailers for that, there's not much change from four hours.

The general consensus is that lengthy films are the fault of self-indulgent directors who studios dare not suggest need the guiding hand of a good editor. And it's true that movies over the 150-minute mark almost always have flabby, unnecessary sections where popping to the toilet isn't going to be fatal. But perhaps these increasingly lengthy films are actually our own fault. Take a look at the Top 10 list of the highest-grossing films, and we're encouraging the epic rather than shunning it.

Only two films in that list are under two hours: the peerless Toy Story 3 and Alice in Wonderland. Of the rest, only two are under 150 minutes and none are more than 13 years old. The fact is, in an age where studios struggle to get people to go to the cinema, a simple two-hour tale would, it seems, be shortchanging our expectations. There is a precedent. Gone With the Wind was, for its time, the longest American film made with sound - though 1939 moviegoers had it easy; the 238 minutes included a four-minute intermission. Still, the public who saw the first preview apparently begged for it not to be cut shorter. As the decades passed, South Pacific (1958), Ben-Hur (1959) and The Godfather (1972) all tickled the three-hour mark on their way to box-office success.

But then something rather interesting happened. The age of the blockbuster, which essentially began with Steven Spielberg's Jaws in 1975, ushered in films that administered a short, sharp, shock. Rocky, Star Wars, Grease, Moonraker, The Empire Strikes Back, Raiders of the Lost Ark and ET were the highest-grossing films for seven consecutive years between 1976 and 1982. None were more than 126 minutes. And perhaps that's why they've remained classics. This was pithy, edge-of-your-seat film-making with no added fat. CGI and 3D weren't such a big deal that directors had to fill their films with acres of them to look cool - at the expense of storytelling. No surprise, then, that by the time George Lucas got round to finishing off his Star Wars prequels years later, they had gone up in length by half an hour.

But CGI doesn't count as an issue for Sex and the City 2, whose bloated running time was widely berated by the critics. Perhaps every one of the 146 minutes wouldn't have been so noticeable if it had actually been funny, but SATC2 was incredibly boring. And that's the real crux here: length is only an issue when the film itself is flawed in some way. And for every King Kong - three hours of my life I'll never get back - there's There Will Be Blood. Lest we forget, this is a film that doesn't have any dialogue at all for the first 14 minutes, and yet every shot seems both crucial and thought-provoking.

Still, they've all got some way to go before Cinématon - the world's longest film at, wait, for it, 150 hours. That's six whole days. It took the director, Gérard Courant, 31 years to make. Let's hope Cameron doesn't start getting ideas...