Storylines can take varying amounts of time. But, since I've got nothing on my schedule until late June, I expect to make a fair bit of progress before then.
The real problem has been that we keep on thinking of ways to expand the story and make it more interesting, thus drawing things out. In my original plan, a certain event was to happen almost immediately which kicked things off; instead, that event has been expanded into the entire part 1 storyline, which is over 20 main-line missions long already, and likely to go another 10 at least.
I've always been about keeping expectations low with EVN Firefly, thus avoiding unreachable goals, and that philosophy has served the project well; but since it is primarily a story-based TC, I make an exception for that.