The lengths of my posts vary to a certain degree. I have certainly never posted one quite that long. It's just not my style, and besides it would take a long time to write it. I might as well be writing a story if I'm going to spend that much time typing. I would say it depends upon how the post flows. A post of 100 words may be adequate in most cases, but if the words are not chosen properly or the content is not good, the post is unlikely to catch the attention of the reader. Rather, they are likely to skim it and move on to the next one. I would say anything more than 2,000 words for a post would be too much, but again, it depends on the content and the flow of the words.