I'm in a similar predicament for a business application. We've resorted to the "scream test". When there are features that are expensive to maintain that we su

I'm in a similar predicament for a business application. We've resorted to the "scream test". When there are features that are expensive to maintain that we suspect aren't being used (based on surveys, interviews, and usability tests) then we insert a notification when the feature is used announcing it's pending removal in some subsequent version. The notification includes contact information so if we get a higher-than-expected number of complaints then we may keep the feature.