We go through 1 to 2 heads of garlic per week. It's essential in Italian, French, Mexican, Greek, Chinese, Thai, Indian, BBQ, and just about every other main dish, side dish, soup, or casserole I make. And if a recipe calls for 2 cloves, I use 3.
Love garlic, and it's good for the heart, too!
As for onions, I probably use an average or 3 or 4 per week. I can't imagine cooking without it. Why would anyone want to eat a hamburger or taco without raw onions?