If a batch is different enough to warrant new reviews, it's a different product and should be sold as such. Consider beer and wine. Industrially manufactured be

If a batch is different enough to warrant new reviews, it's a different product and should be sold as such. Consider beer and wine. Industrially manufactured beer doesn't vary much from batch to batch, so it's sold by brand. Wine varies a lot from batch to batch, so it's sold by brand and year.