Way Around Building Lighting When Saving Current as a New Level?

If scene has Lightmap, it seems I have to re-build lighting when I use Save Current As (level).
Since I have no need to rebuild lighting in certain instances beyond “Level_1”, is it okay to just back up (as in file-copy) and then rename as something else (ie “Level_1_Copy” to “LeveL_2”, or will this mess up dependencies when loading in this new level. ie - will it only work as “Level_1”

Thinking might work as a way to not have to build a veracious lighting again and again just to get a Level_2 with lighting that exactly matches Level_1.