About once a week. We're more concerned about the impact on our waist lines than our finances.
One thing we try to do to save money is to order meals for leftovers. As an example, a $14 burger will almost always be one meal, while a $14 Thai curry typically lasts for 3 meals or more. Even within specific restaurants, bowls or plates offer more bang for your buck than sandwich entrees.
We also often roast vegetables or other side dishes in the oven while waiting for delivery, mainly for health but it's also typically cheaper.
I want to start doing more oven roasting, but my oven takes absolutely forever to heat up. I've even replaced the coil inside of it (electric stove). I've been debating on buying one of these new stoves that has two ovens, like a tiny one that should heat up fast and then the bigger one.
We bought a countertop convection toaster oven that preheats within ~5 minutes. As a family of 2, it has pretty much replaced our oven usage, but a larger family might not like it as much. It can fit up to a 9x13 pan so that's a small sheet pan or most casserole dishes.
It's really nice that it doesn't make the kitchen hot. It can also air fry decently, not as nice as a standalone air fryer, but it's way more versatile. Ours is a ~ $300 Calphalon, pricier than most, but we use it almost daily, and the cheap Oster one we had before only lasted about a year. I'm sorry this sounds like an ad.
No that's fine, I have a Ninja grill/air fryer combo and I use not all the time. My wife has a set of Calohalon pans that she really likes, so I know they're a good brand.
Also consider a toaster oven. They come in sizes up to 12" or so, definitely big enough for 9x11 pans, and the small chamber means they heat up super fast. I have a gas range, but I keep an induction hotplate on top of one burner and a toaster oven, with convection, in the next room for smaller jobs. Keeps the CO2 and the heat down in the summer.