I think it depends on how strict the cops want to be and enforce it. I drove my challenger around for 2 years everyday when my old cj5 was torn apart. I was never stopped for running with historic plates. My dart has historic plates, i don't drive it everyday but in the summer i take it out 3 or 4 times a week and have never been stopped.
97 tj, 4.0l, hp30/44, 4" tera, 33" trxus, homemade bumpers and on board air.