code: function(channel, numDays, next) {
      var filter,
        modelName = this.getDataSourceName('dup'),
        maxTime = (new Date()).getTime() - (numDays * 24 * 60 * 60 * 1000);
  
      if (channel) {
        filter = {
          channel_id : channel.id
        }
      }
  
      this._dao.expire(modelName, filter, maxTime, next);
    }
docs: expires duplicates