Fascinating!
I go to the grocery store once a week, and probably once a month I will go to Trader Joe's and once or twice to someplace else (the farmer's market, specialty store, etc.) If I run out of something in between times, I pretty much make do unless it is toilet paper or some other vital supply. (Ie, the milk went bad earlier than I expected, so this week I'm using almond-coconut milk on my cereal that was bought for a different recipe.) However, I tend to do all the shopping in one trip and plan it all together, so even if I'm making different stops it feels like one trip.
Back when I was car free, I probably shopped a couple of times a month because dragging everything home was such a hassle, even with a cart (my neighborhood was quite hilly).