Havng finally found original MitsubishiI service information for the Mitsu MIVEC-type engine (which our 3B21 is), I noted an interesting thing: they schedule a filter change every OTHER oil change (and the normal service OCI is 7,500 miles, not 10,000). The normal OCI for 3B20T turbo MIVEC in the Mitsu i car is 6,000 miles.
That said, I plan on continuing with my severe service, 5k + filter regimen.