I would suggest replacing them every time. Such a small part can cause severe damage and worst case scenario your car catches fire. Not to mention it is a lot of work in case they leak if reusing them. I am actually setting up a business selling o-rings called [ www.oringking.com ] The business isn't set up yet but I am going to start out selling o-ring kits for Fusion guns and the P2 gun for spraying urethane's since those guns have to be broken down and o-rings replaced after every use. I will also have kits for 300zx.
