I have two cats as well. One is very old, and mostly sleeps. Even when she was younger though, she would stil be able to walk on my hobby shelf among my models and not disturb a thing. She never chewed on anything or tried to play with it. She seemed to know not to touch any of my models.
My other cat is a tgerror. He knows not to climb on the entertainment center, but I always know when he does because some solar panels come off my Babylon 5 kit, and several other things are moved around. Since we 'cluttered' the top with more stuff, he hasn't gone back up there.
On top of my desk hutch we don't have enough things to 'clutter' it up, so I tried leaving sufficient room for him to walk and/or lay down without disturbing anything. It worked, but then I hit the desk, and now my Calypso is in pieces!
My other 900 or so models are in the second bedroom of our two-bedroom condo which always stays closed and no cats are allowed in. They both know it, but my one younger cat just loves me so much he still tries to get in to see me. When he fails, he just sits right outside, as if guarding the door for me.