Tag every request
Use one tag for feature requests plus a short label for the feature. Consistent labels are what make counting possible later.
Count the demand
Review the tag each month and note how many different customers asked, and how important they are. Volume and value both matter.
Offer a workaround when one exists
A clear workaround solves today's problem even if the feature never ships. Save it as a reply for next time.
Close the loop when you ship
Email the customers who asked. It costs little and shows that asking was worth their time.