That is the length I go for. When I feel done, I am done. It is so freeing. No one is paying me to get people to read this. Sometimes (often) they don't read it. I know I am such a reader myself after all these years. I learned to try and keep everyone in the loop so they know I still think they are relevant and read them as much as I can.
I guess it depends on the subject. If it's something in which I'm interested, I will probably skim through the entire post. If it's something that could be answered in a couple of sentences, but goes on forever, I just move on.