CONTINOUS COPY PASTING SLOWS DOWN WORK PROCESS

Hello, 

this is the scenario:

lets say i created 8 ai files andkept it as stock (e.g file 1 dining table with chair, file 2 chandelier, file 3 window with curtain,... and on)

now i want to create a dinning room in 1 illustrator file. which will have all the other ai files (file 1 dining table with chair, file 2 chandelier, file 3 window with curtain,... and on)

i tried to drag the ai file directly from explorer, but it places it as image.(failed,I NEED ALL THE DRAWINGS IN VECTOR FORMAT WITH ITS LAYERS!)

SO NOW I HAVE TO DO THE LENTHY PROCESS OF COPY PASTING i.e.

i open window ai file and copy everything (all the layers: window frame, window pane, curtain left, curtain right, sky)

 I do same with other files and paste it on my new dining room file and rearrange resize them.

It takes hours to do this and if file size is big, illustrator hangs slows down.

Is there an easier and faster way? Please respond urgent