It's economics. If I buy half a gallon of half and half, I know full well I don't need half a gallon for my coffee before it spoils. I estimate that between 40

It's economics. If I buy half a gallon of half and half, I know full well I don't need half a gallon for my coffee before it spoils. I estimate that between 40% and 0% of it will be wasted on average depending on how many weeks it lasts in the fridge. But if I compare it to buying a quart, a quart will cost me around $2.49 while half a gallon would cost me $3.79 This means that for a cost of $3.79 I get to use 0.4 gallons on average, while for $4.98 I get to use 0.5 gallons (assuming a quart never expires, which isn't true, I've had a quart go bad after a little over a week) This means that for 0.4 gallons buying quart by quart I have to pay 3.98, but buying half a gallon I pay less. So my strategy is then to buy quarts when they're on sale (when I can get them for $1.99) and half a gallon when I have no discount.