I've also been told to keep the keychain light -- better yet, use a
single key for the Benz.
I've actually seen a worn out key (use the new one that comes with the
new tumbler, get one for the old cars) after 30 years and 200,000 plus
miles, but they are rare. More than one sticky tumbler has been
"cured" by getting a new steel key from MB.
The other advice I've been given is to NEVER use a brass key from the
hardware store or a locksmith -- they shed small slivers of brass since
Benz designed those tumbles to use steel keys (and last forever!). The
brass shavings will jam the pins in the tumbler, causing it to seize.
Peter
