I don't have customers come back bitching that their tires are leaking when I don't install new parts that aren't needed. I have happier customers because I just saved them $100 on unnecessary parts. Not trying to get into a pissing match here, or tell you how to do your job. What I'm trying to say is sure, put an estimate together for each car showing that they will NEED the parts POSSIBLY. Then once you get the wheel apart inspect the grommet for tearing/deterioration. Then sell them the new part, if need be. Each car should be different, some will need them while others won't. Know what I mean?