On most cars ive worked on ive replaced the coils as well, or they ended up getting replaced because of getting lowering ones etc.

Sometimes the coils actually do need replacing, example on the pathfinder my parents have the back springs are notorious for sagging after certain mileage.

And coil springs break as well..

Had a 01 a4 quattro 1.8t i sold but the rear coils were known to snap, on mine a peice actually snapped off at the very bottom it didnt affect it because the spring couldnt move around and was still set.

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2006 X5 4.8is Fully Loaded