I have spent a lifetime in computing and know the ins and out of projects which are thus: 1) Give a low estimate and short time to get the job. 2) Begin with enthusiasm. 3) Wait for customer to change/add to the spec. 4) Give increased figure because of changes. 5) Give delayed end date due to changes. 6) Continue to give upgraded cost and time estimates due to failures/changes by others or 'unforeseeable' problems. 7) Repeat 6 until customer become suspicious. In short, keep the job going as long as possible because it means more dosh for the contractors.