interesting topic, i have a wide range of cooking times and firmness when done. since i do like the variety among all the beans in textures and flavors i try to keep an idea in mind of what i want as a result when i use certain beans.
at the moment i have a type of bean which is fairly small but it works great in chili as you can cook it for several hours and it won't fall apart and stays firm. very hearty to me and i use it as a meat substitute or filler (so i don't use as much ground beef) when making chili. then i have other beans that are quicker to cook and have a very mild flavor and are creamy in texture, they'll cook in an hour or so.
it does seem that age also matters when cooking beans. i still like them no matter how long it takes to cook 'em.