That's normal. I usually go through 3-4 gallons myself. I don't like to stockpile it though so I usually end up with one gallon at the end of the year and then I just add a bit of water for the summer. Diluted windshield washer is better at cleaning than pure windshield washer fluid. A few times I've been driving in the snow and want my headlamp washers to kick in, but there's no button for it, so I have to use the windshield washer fluid more, it only comes at the 5th use of windshield washer fluid with the lights on. At least mine holds more than a gallon, when the warning light on low windshield washer fluid comes on, I can toss in a whole gallon and then get rid of the jug. In previous cars, they only held 3/4 of a gallon so you'd have 1/4 of a gallon sitting around taking up space.