Our newest cat would eat all day if you left food out. We found this out the hard way, and we are still working his pudge off. Hazel wants his food promptly at certain times of the day, Rhiow is a grazer, Oscar loooooves his food a bit too much. When we first got Oscar as a kitten, he was very sick, and extremely thin. You could see every bone on him except his tail,which was too fuzzy and hid the bones. (Instead of being filled in, his flanks were concave. I really worried he would die on us, but we took shifts with him, and at any sound he made put him in front of the water dish, food dish and litterbox to see if that was what he needed. He was too sick to get himself to the food dish at first.) It took a couple of weeks, but he got well enough to get to the food and water on his own, though he had a couple of accidents in not making it to the litterbox in time. We forgave him because he was still sickly.
Anyway, after noticing that he was eating all the food when there was one bowl we got seperate dishes. Then we noticed that he would eat all his food, then go over and eat all of Rhiow’s food, and that if he couldn’t finish it in one sitting he would come back a bit later and do so, then he would move on to Hazel’s dish. Rhiow was losing weight, though Hazel eats his fill at mealtimes, so he didn’t. So, now we only put out food at certain times of the day, and note it down so Oscar doesn’t “con” the other human into giving him an extra meal. (Which he promptly began to do once we started regimented meals.) Needless to say, Rhiow the grazer is having to learn not to be one. At least she has gained the weight that she lost back. Obviously not all cats are like this, but why not go ahead and get two food dishes anyway? This way you can also know more easily how much each cat is eating, so you can pick up on the fact that one cat might be sick sooner.