Or you could buy lots-and-lots of grape juice and make it an annual occurrance. I don't think that grape juice has that short a shelf-life that a monthly trip is required.

The immediate limiting factor is the amount Asda has on the shelf at once.

(The limiting factor after that would be the amount of my kitchen I want to give over to storing my long-term stock of grape juice.)

Or make an order, etc. (Though still limited by space depending how much you drink.)

Or drink wine, and uh, I don't know what.