I'm a steel freak. I have a '84 Trek 610, a '80 Masi GC, a '80 or so Mondonico, and a (dang!!) '80 Woodrup. Each one rides different. If I didn't have a better fitting and (just have to say it) better riding Mondonico, I'd ride the Masi all the time. The Trek and Woodrup have their places. For example I can't fit fenders on the Masi, and the Mondo doesn't even have eyelets.

So yes, ride your classic bike all you like. You really won't hurt it unless you crash.

Road Fan