blender array modifier and lightmaps

i am modeling this building in blender wich consist of a set of three floors,the set of three represent the windows placement variations
after that i apply an array modifer with a number of 4 to get 12 floors in total

also i make the holes for the windows with booleans modifiers, please look at the attached image to get better a idea

now my question is :

**do i have to make uv lightmap **
- for each floor ?
- to the set of 3 floors ?
- or apply the array modifier and make the lightmap uv of the whole building ?

thanks and good day/night