The number of proverbs in the Chinese language is quite staggering. I have a ten-volume collection of all the Chinese proverbs and a different story behind each of them. However, there are rare ocassions when the proverbs have three or five characters. They sometimes teach morals on life, mostly of the Confucian style. You know, filial piety and all that.

The four-character phrase was very popular in medieval Chinese, especially in old epics where people would convey entire paragraphs using nothing but a string of four letter sentences. That was considered very "eloquent", however, it does make it sometimes ambigious and hard to read and understand. I read the old version of Romance of the Three Kingdoms, took me ages to get through. It was compact though, I'll admit that.