I don't think the size is "too large", but just that you don't go quite often enough. Perhaps if you shared some more information - such as what diet is like (certain foods you eat a lot of, which foods you avoid, do you eat a lot of fiberous items, do you restrict fatty food or do you eat a lot of fat), how much water you drink each day, what other drinks you drink (particularly caffienated drinks or alcohol), and any exercise habits you may have - this could help others assist you.
Obviously the intestines can hold a large amount of poop. The less often you go, the more that will need to come out when you do go. I have had some 2 footers on occasion!
I've never clogged the toilet, though.