I've only ever participated in advanced RPs and there are plenty of people there who understand that quantity doesn't equal quality. It varies a great deal, if there is a lot of dialogue for example, post length is necessarily short, though I usually get around this by empowering my partners to take conditional control of my character. We have discussed the themes and there characters ahead of time so I can have a reasonable expectation that they will use my character in the correct spirit. If not I ask them to rewrite or allow me to suggest what my character would actually do (this has never actually come up). Sharing control of characters at a fairly superficial level allows you to move through dialogue much faster and makes it easier on everyone. That, to me, is what advanced writing is. We trust each other to work in the interests of the story and not myopically focus on our own characters.