Preface by saying, I think this thread should be in the promo subforum. Just caught a glimpse sign out at my local Napa for the 40% off 'Gold' filter sale either this coming week or next.
That said, as many/most Napa stores are franchised these sales tend to be very local and timing differs. If you have some Napa stores in your area, you might stop in and ask if they have a sale. Example, here closest local store, franchised, has the Gold sale twice a year spring and fall. The next closest store with franchised stores in NC and Va. has had them occasionally, but not seen one in last couple years.