I think it depends on scale and the inertia involved, and my original point was that accurate estimation is possible.
There are many other challenges as you point out.
I am currently on year two of a five year project. The key (and part of the essential difficulty) is finding quarterly or six month valuable deliverables that help ease anxiety of everyone involved.
It is not easy, but it is possible.
While all this is going on, I'm also working on a design document for a potential 10 year project. I doubt that I will pull this one off since I'm having difficulty finding those quarterly deliverables, but I'll keep grinding away.
There are many other challenges as you point out.
I am currently on year two of a five year project. The key (and part of the essential difficulty) is finding quarterly or six month valuable deliverables that help ease anxiety of everyone involved.
It is not easy, but it is possible.
While all this is going on, I'm also working on a design document for a potential 10 year project. I doubt that I will pull this one off since I'm having difficulty finding those quarterly deliverables, but I'll keep grinding away.