Sienna's on raw, and usually only gets dinner. Before I switched her, when she was eating kibble, she never ate her breakfast so I just stopped feeding it. Dinner at my house tends to be late, but she usually gets something else during the day - frozen kong if I leave her home alone, sometimes an egg in the morning, training treats, my lunch leftovers...and sometimes helps herself to the cat food when I'm not looking. (Bad dog!) If her dinner was something with a large-ish bone, she'll work on that overnight and during the next day.
My parents' ACD gets breakfast and dinner, but usually doesn't finish the meal so she always has food in her dish.