Hi Lecra,
of course everybody will find his own workflow fitting to the style of work and preferences. The UV-Processing is basically required if you want to add a texture to your object to place it properly and in the correct scale.
(1) If you have objects you simply want to add a Maya material shader or a mental ray material with solid colors and without any texture of course you don't need to unwrap the UV.
(2) For each different object you should have a own map, only if objects are similar in shape and size and supposed to have the same texture you should transfer the texture information from one object to the next object.
(3) like said, you can model the scene complete and then transfer the UV to similar objects, for example you have 4 similar wooden chairs, you do the texturing at one chair, then you transfer the UV under Mesh (Polygon), transfer Attributes, make sure, that the UV Options are ticked