I'd be tempted to say that a lot depends on being clear on what needs to be achieved. I've personally seen deadlines slip mostly for the lack of clarity on wha

I'd be tempted to say that a lot depends on being clear on what needs to be achieved. I've personally seen deadlines slip mostly for the lack of clarity on what needs to be done. An analogy might be to say that what was initially described as an elephant turned out to be a giraffe. Of course, there are instances when the actual approach, implementation or choice of technologies tend to weigh. But the latter is much less frequent.