Sometimes the presence of oil stains running down the shock body starting where the shaft comes out of the cartridge, tells you that they're giving up the ghost. The test you tried doesn't say much unless the shock is utterly shot. Nor does that test where you stand on the bumper and try to bounce the car. How did the car feel at highway speed ? Would you have lost control if it had swayed to avoid a child running into the street ? Original struts from a 1990 ; that is really a long life for a strut. With your new struts the car probably turns a corner and seems to remain flat and not ride like a marshmellow. You did the right thing also if you carry passengers in the wagon up to seven? I put in Bilstiens and those things are very "serious" but very stable at highway speeds