Sometimes I'll run in for just cat litter and a bag of coffee (the local ones carry a regional brand of whole bean coffee that's okay for the price).

We have both Sam's and Costco (we generally get different things at each), and they are just a couple of blocks apart, so if our bi-monthly shopping is heavy to one, I might only need a couple of items at the other.

I actually do sometimes depending what it is. For instance I'm low on kosher salt and we cook a ton so we only get it at Costco, I'm gonna stop by later this week for a box.

I absolutely loved people watching in the food court where people would go there for a $5 roast and a $10 bottle of wine and that was all they came for.

I live in a rural area and my closest Costco is over an hour away. I go once or twice a month, usually when my husband is in town for work, we get everything we'll need for that month since we're not going often. If I were closer I'd go all the time because I love it there and I'm one of the lucky ones, mine is never crowded.