i hope you meant paint. If you put primer on as a top coat (over other primer), then drive it, you're probably asking for trouble. Primer absorbs moisture, so it'll rust out real quick, the speed depending on what's under the primer. Then if you ever do want to refinish the right way, you'll have to start over from scratch (or worse). Flat paint may have a similar issue, i'm not sure.
Edit: I just saw, you're in ca. Maybe it won't be so bad out there. Still not good, but you're way better off in ca!!! Lol, i tend to think wi/midwest issues!
