Questions about recipes for and their ingredients for dogs?

How much a dog can eat of certain types of foods is directly proportional to their body size. For example, the 3 dogs my family has had for 12 years now have had chocolate at-least once a week for 11 years of their lives, sometimes once a day for a week straight. They are all still healthy, no arthritis or anything, and they've even been fed the cheap old ol' roy and others similarly as cheap from Walmart as their primary source of food when they're not being fed people food. If your dog(s) is/are small, I'd suggest doing a lot of research before conducting such experiments with their food, but if they are bigger dogs atleast 60 pounds or more, I wouldn't worry too much.