My motto is:
Drive it until it breaks, then fix it. Then drive it some more.
This hasta be done with a certain attitude, you have to check the fluids n' things, keep an ear out for strange noises, and depending on what engine you have, it wouldn't be a bad idea to have some spare parts lying around. You also need to get ready mentally for when it has a sudden hiccup/breakdown. It will put a kink into yer plans... cuz now you gotta fix it, unless you have another vehicle you can roll in.
But then, my '65 is rustin' and beat up anyway. She runs pretty good tho'.
-W