I'm sorry for going against the conventional wisdom here, but if the shocks are original, then they are quality units and could very well be in good shape after a few hundred thousand miles. Just because they have high mileage does NOT mean they are gone.

It depends on road conditions that they have lived with. If they are aftermarket and not Bilstien, then they very well could be shot. As psfred said, they are worn out when they are loose and knocking. I've seen Bilstiens with almost 300,000 miles in such good shape that you couldn't tell the difference after replacing them.

On the 123 the shocks are very easy to replace, so I would loosen one end and give them a shove. If they are not rattling and still have pressure, leave them alone.

My $0.02,