As Harry Potter racks up its 15th hour of celluloid adventure and the Transformers battle it out for two-and-a-half hours, Mike Goodridge is watching the clock.

How much does running time affect box-office gross? Conventional wisdom has always had it that a film should run to two hours or less to allow more daily showtimes at the multiplex. Naturally, a three-hour film will have fewer showings each day than a two-hour film.

Let’s not forget that when directorial hubris meets big budgets, the results can be disastrous. Meet Joe Black, The Postman,Heaven’s Gate… need I say more?

But as if anxious to deliver more bang for the admission buck, Hollywood studios are going longer with their tentpole movies in an effort to entice audiences to a true event experience. The season’s biggest hit,
Transformers: Revenge Of The Fallen
, ran to 150 minutes of robotic combat and explosions; its greatest box-office challenger, Harry Potter And The Half-Blood Prince, is a tomelike 153 minutes.

For that matter, looking at the all-time box-office rankings, recent event movies such as The Lord Of The Rings and Pirates Of The Caribbean trilogies show that audiences will happily engage in an immersive storytelling experience that might entail one or more loo breaks.

The critic in me, however, becomes irritated by unnecessary length. I can understand, even appreciate, the need for film-makers to stay true to Tolkien and Rowling and satisfy the devotees of the novels. Indeed Potter fans turned out by the gazillion to the opening of the new film last weekend, sealing their endorsement of these faithful adaptations.

But am I alone in getting a little bored at the episodic nature of Harry’s battle to bring down Voldemort, this time peppered with long stretches of teenage romance? The Potter films are sumptuous and beautifully produced but so slavishly faithful to their source that their talented directors have been unable to exercise the cinematic license that the film medium requires.

I still feel I’m more riveted by the journey of Dorothy in The Wizard Of Oz (101 minutes) or Elliott in ET: The Extra-Terrestrial (115 minutes) than the 15 hours of Potter adventures to date.

As for Transformers 2, I confess to a nap during that one, though the loss of 20 minutes in the middle didn’t seem to affect my understanding of the plot. Like the final Pirates movie, At World’s End, the aim seems not to tell a tight and gripping story but to showcase as much CGI work as possible.

Last week, I saw Funny People, Judd Apatow’s new comedy which runs to a massive 140 minutes and crams in so much that it felt like Apatow was combining multiple scripts into one.

I know it irks film-makers when critics complain about length, even more so when they suggest what could be taken out, but Funny People really does feel undisciplined and indulgent. Which is a shame, because it also includes some of Apatow’s best work to date. A good narrative can be diluted by extreme length, a mistake which Hollywood has, until recently, been expert at preventing.

Transformers’ running time clearly hasn’t bored fans who have driven it to grosses of more than $725m to date. But as these movies become longer, film-makers need to be aware they may turn audiences off. Let’s not forget that when directorial hubris meets big budgets, the results can be disastrous. Meet Joe Black, The Postman, Heaven’s Gate… need I say more?

Ironically, Hollywood’s cousins in Bollywood have been shortening their tentpole pictures. A Bollywood blockbuster has traditionally run to at least three hours, catering to a different theatrical experience which sees people wander in and out of the theatre for snacks and nose-powdering during musical numbers. But current hits Kambakkht Ishq and New York run to 142 minutes and 153 minutes respectively, showing a desire to reach wider international audiences.

So, as Bollywood shortens, Hollywood lengthens.

I maintain that the art of a good storyteller is to be disciplined and efficient in his or her chosen medium. If Pete Docter and Pixar can tell the multi-tiered story of Up so elegantly and eloquently in 96 minutes, what’s wrong with short?