Duplicating a Mesh in Unity vs importing a full mesh from 3ds Max

Hi

There are three parts to this question. I am creating a third person game where the character walks through a property which has 5 towers and over 20 floors in each tower. There are about 8 balconies for each floor in each tower. I have a script to take the character to any of these balconies for a view from there.

Now my first question,

As floors above the first floor in each tower is a duplicate of the first floor, would it be
a. Better to import only Ground and First Floor from 3DS Max and instance the other floors from First Floor inside Unity,
b. Import all the floors from 3DS Max.

The Second question (if Q1 a is true) is - Since these are static meshes, should I then
a. Instance these in the scene itself or
b. Instance them at run time

And if the answer to Q2 (a) is true, how can I do this with a script.

Trust I have been able to explain my case properly. There will be no destruction of any tower/floor in the game at any point.

Best Regards
GP