Actually theres no reason why you couldnt build 80 towers in 2 years ... just comes down to having the right amount of resources.
2 years to complete one tower is plenty of time so you just need 80 teams working on it!
It's that kind of thinking that has lead to the long delays in people waiting to take hold of projects.
I can assure you, it simply doesn't work that way because of:
* finite resources - you can't simply multiply the order by 80.
* Labour - obtaining, training and coordinating
* Project Management
* Quality Assurance
* Financing
All these things compound to create problems.