ArenaSnow - Oh, I definitely agree that the actual content is more important than the length. Quality over quantity. I think the only reason I end up writing such large posts is because my setting is very complex fleshed out and so without a lot of details the points and quality of a post would be lost in transition. It's sort of like how a movie will usually always be a really dumbed down version of a book's storyline that lacks its depth and doesn't feel as detailed. I'm something of an extreme perfectionist when it comes to details. The only other reason my posts end up so long is because I like to write very heavily into my character's thought processes, due to having an extensive interest in psychology.
Most of the best role-playing topics, or sessions I guess you could call them due to so many being over IM, actually did come to some sort of conclusion, but since they were all using my main story project's setting, they obviously felt more like the end of an "arc" or an "episode" instead of the end of a "series" or "franchise". Still, I definitely know the feeling of investing a lot of time into something and then lack of devotion on other people's ends caused it to all be a waste. I've had a few forums end up like that, and that Final Fantasy RP forum I told everyone I got my start in text-based role-play with actually had the same problem, multiple times. I poured well over a year one time into helping rebuild and flesh out its mechanics and systems, only to see most of the members abruptly disappear for seemingly no good reasons. Obviously, since I always work with my main project, I haven't had to worry about feeling like my work was a complete waste since it always contributes to the main project when its one of my own forums, but it can still be annoying.
As for what you mentioned about becoming an author yourself, that's an interesting dilemma to have. I honestly don't have that problem. The issue I have that causes me to keep nitpicking my work is that until I sort through my thousands of notepads and create a proper database for my story, I'm never satisfied anytime I attempt to write a sample of the work for people to see. So even though a large portion of the story is written in my head, until I get all those details collected and sorted, I can't really go anywhere with it. If putting other people into the equation does anything for me, it motivates me to be more productive so I won't procrastinate getting somewhere, because constantly having literally years of work get lost from technology screwing up can really do a number on a person's morale. I feel like I'm off topic though. There's probably some other place I should be saying this sort of thing.