Once a week for our main meal-planning trip; a second for any fruit/veg to finish out the week.
The weekly meal plan takes into consideration things I want to use up first.

Weekly to a local grocery store for produce, milk, etc.

Monthly for Costco. My freezer is full of proteins (chicken breasts, chicken thighs, shrimp, apple chicken sausage, ground turkey), kids snacks (various granola bars, dried fruit), and paper towels, tp, etc

Also monthly or every 6ish weeks to Trader Joe's to stock up

Occaisional trips to a nearby grocery store for an ingredient I don't have for something I decided to make.

When I could walk 1 block to the grocery, I ordered delivery for heavy stuff and did mini trips nearly every day. Now that I moved out the city and drive to the store, I tend to do a big weekly shop and two or three mini trips.