It's an all-you-can-eat buffet. You don't have to eat all you can. The most effective way to combine these sentences would be: It's an all-you-can-eat buffet. but you don't have to eat all you can. It's an all-you-can-eat buffet, and you don't have to eat all you can. It's an all-you-can-eat buffet, so you don't have to eat ally you can.