A long gestation period and major reworking of a film can often spell trouble. Cutthroat Island (1995) or The Lone Ranger (2013), anyone?

But at critically feted and box office- conquering Pixar Animation Studios, working on a film for five to six years with a major overhaul or three along the way is par for the course.

The Good Dinosaur, which imagines that the creatures never became extinct, was initially slated for release in May last year. It will now open in November this year, "completely changed" from its earlier incarnation, says Pixar's president Jim Morris. He was in Singapore for internal meetings along with Disney Animation Studios' president Andrew Millstein and they spoke to regional media separately at Four Seasons Hotel Singapore on Tuesday evening. Pixar was acquired by The Walt Disney Company in 2006.

Mr Morris, 60, says: "There was a fundamental flaw in the story we were trying to tell and we couldn't figure out the right way to fix it. It wasn't that it was a bad movie, it just wasn't a great movie."

And "not great" is not good enough for Pixar. Bob Peterson (Up, 2009), who came up with the idea for the story, left the project and his collaborator Peter Sohn was officially announced as the new director last October.

The process of knowing when things are right is akin to falling in love, says Mr Morris. "You know when it's real, you just do. All your emotions are wrapped up in it. And when it's not quite right, you kind of know that too."

He points to other beloved titles in Pixar's body of work - comedy adventure Toy Story 2 (1999), fantasy comedy Monsters, Inc. (2001), space adventure Wall-E (2008) - and says that they had long and laboured journeys.

The upcoming Inside Out (this June), about what goes on inside people's heads, was also "a complicated subject matter to try to figure out".

The lesson distilled, he adds, is: "We pick film-makers who seem to have a unique story to tell that's driven from within."

The mantra that passion for the project comes first is also key at Disney Animation.

The success of Big Hero 6 (2014), particularly in Asian markets, is partly due to its strong Japanese influences, from the setting of San Fransokyo to the key characters. It does not mean, though, that Disney is rushing to include an Asian angle in its upcoming projects.

Mr Millstein, 54, points out: "It reinforces for me that great stories will work universally independent of the specifics of any particular story. To me, that's the lesson. Be diverse in our storytelling and make great cinema."

After all, superhero-themed Big Hero 6 played well outside of Asia and European-fairy-tale- inspired Frozen (2013) "worked fantastically" throughout Asia.

He adds: "The strength of Big Hero 6 for us was that it was a story passionately developed by a director who was interested in it. It reinforces our approach, which is you really bet on the people and their ideas."

The film was directed by Don Hall (Winnie The Pooh, 2011) and Chris Williams (Bolt, 2008).

Next up for Disney is Zootopia (March 2016), where animals live in a modern world designed by animals, and Moana (November 2016), a musical set in Polynesia featuring a female protagonist.

While Pixar and Disney Animation share similarities in their values, they also work on projects independently given their different histories, cultures and aesthetic sense.

As Mr Millstein puts it, they are aware of what each other's stories so as to avoid an overlap in the movies they put out, but "we're not working on each other's stories".

But at one point in a project's life, it gets seen by fresh eyes.

Mr Morris says: "One of the great benefits of having a sister company is that we can all see things that don't work in movies, but sometimes we don't know how to fix them. And they'll make suggestions and vice versa. It's terrific to have that and we use it."