My understanding is that if they are not leaking, they are ok. The "cushion" is provided by the accumulators/spheres. The accumulators are easily tested. Hopefully you may just have an issue with the ride height setting on the control valve. There is a very good thread on how the system functions as well as testing and adjustments. I cant remember if its on this site or the "other" site under the w126 forum.

John