With enough wear & tear, especially around the pesi hole, they tend to break.
Then again, there are sellers who scrap, for example, a damaged scabbard because they feel they get a better price for a nekkid keris of quality rather than for a compromised ensemble...
I understand that one might wish to keep a keris in impeccable fittings for cultural reasons; however, destroying pieces of art because they are damaged/worn, also destroys cultural legacies.
Restore if needed but keep any older bits & pieces with that keris/etc. to preserve the full cultural & historic legacy! Keeping pre-restoration pics is an essential requirement for professional restorers and mandatory to pass on along with any pieces that have been worked on (cp. rules of conduct for any professional restorers' association). I'm still waiting for the first antique dealer in keris (or SEA blades in general) to adopt such a professional stance!
Regards,
Kai