3D Symbols

[Baz]

Hi all
I have a concept plan of several buildings on the same site and the drawing is getting quite unwieldy.
I have seen mention in the forums of making symbols to cut down drawing size and have done a fair bit of searching to find the answer to my specific question.
Is it possible to convert a building to symbol and still retain all 3d data?
I suppose what I'm asking is can I have my whole concept drawing made up of all the buildings (as symbols) so that I can show the client without having to wait forever for the drawing and camera views to load (and still have the ability to rotate the views.
If so, how do I do it?
I've found the make symbol tool but it's greyed out.
As usual, any suggestions will be more than welcome.

Thanks all
Baz