Hello,
These seals are not designed to be replaced at each oil change. However, the top tubular seal may fall off during oil changes and be accidetally left out. If the technician does not know to look for it, years may pass with the oil by-passing the filter altogether!
This top tubular seal and the flat rubber seal in the canister should be changed occassionally when the rubber becomes hard. One should always check to see if the top tubular seal is in place.
Mercedes engines after this series had all these seals built into the oil filter so they would automatically get changed when the filter did.
Joe Alexander
Blacklick, Ohio