A sad inevitability It is not exclusive to these forums. Everywhere I go in search of roleplay, this will happen.
Apparently though, there is a problem here with making your posts too lengthy. Yes, I have noticed that. For this reason, I prefer more faster paced roleplays with shorter posts, and more encouragement on interaction between players rather than more novel-like affairs. Doesn't have to be a one-liner. I hate that. But like, a paragraph a post is a pretty decent amount. Encourage people to post at least once a day. At least once. I think that's a good pace. More than that would be pretty awesome too, but not too quickly because some cannot keep up.
As a GM, you must be a leader. I realized that in all the mistakes I made in the past GMing. I wasn't enough of a leader. Giving your players too much freedom will cause them to become confused and lose interest. But you also must not make events exclusive to your posting. Because that's a surefire way for a RP to die. Waiting for GMs to post is annoying, and isn't something I've had many problems with until I came here. I do think they have too much control over the events, and prefer them to act more like a player character with a more active role in the story.
If things become stuck or reach a boring point, then it's up to you as GM to get them unstuck to keep the thing alive though. That's the part about giving people a lot of freedom that can get out of control. You reach these points where it's difficult to think of anything to do. A GM must step in and provide something when the RP slows down. Also, don't be a GM if you don't have a lot of free time and find yourself being the person who says "I have work/school, can't post" for a week. A week is all it takes for a RP to die. Only do it if you're sure you can. Don't waste everyone's time.
As for being a player, I have only one recommendation. POST DAMMIT. Stop talking about posting, and just do it. Don't chat, don't make overly complicated plans about everything. Go to the thread, read what has been said, and make it happen. It is a simple task that is often over complicated by peoples' procrastinating minds. I guarantee you that RPs will go faster with more people doing that. This isn't a matter of discussion. It's a matter of getting your ass up and doing something. People need to motivate themselves as much as their GM needs to keep things flowing smoothly.
And if you mess up? Well, who cares? You can fix that later. There's never no going back in an RP. I've edited posts and redone events in RPs several times when I don't like the way it turned up. The important thing above all is getting things done. You can mess around with the small details later.