If you're posting a project that you know you're going to follow-up with additional posts, you should probably post (reserve) some replies in advance so that the thread isn't broken up by replies to your initial post.
For example, I may start a project and post the thread:
"New Project by Chris Savage"
But then I will make several replies like:
"Reserved for part 2"
"Reserved for part 3"
etc.
Then you can edit these posts later to add in the additional content. I hope this helps.