I'm wondering if you can address your requirement via field history tracking. Enable history tracking for the fields of interest and then have a report run off it, which can be emailed (potentially scheduled) to users.
Another possibly way would be to have a workflow fire when any of the fields are updated and then have a task created assigned to the user concerned to remind them to update the fields before a certain date. This however wouldn't apply retrospectively to fields in need of I being updated today.
A third alternative could be field history tracking plus a batch process. So the batch process runs daily and interrogates the history object to check which records on which fields were updated more than a certain time period ago. It then sends emails to the identified records owners.