The bolts are somewhat robust and may be reused if they haven't exceeded the spec on maximum length. I reused mine when I replaced the head gasket. All of them weren't much longer than original length and had plenty of stretch left.

I imagine the spec for max length is to weed out those bolts which may have been over-angled or overtorqued, which can sometimes happen if you're interrupted during the job and lose track of the torqueing sequence or if your torque wrench is off.

I too find it strange to hear the comment "gasket is not blown just dried out". But this is just semantics.

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95 E320 Cabriolet, 169K