At 4500 miles, I would do all four. When having shocks rebuilt is the time to have any changes made in the ride characteristics. Any good shock guy can re-valve them to fit your liking, softer, harder, more bottoming resistance, more transfer, less transfer, etc. Just tell them what you would like to have different and they can usually make it happen and the added cost typically does not add much to the final cost of the rebuild. I have been using Ed - Ingram Motor sports in Paddock Lake, WI and have been very happy with his work.