This thread is very interesting to me, because I’m working on my first trilogy: http://www.choiceofgames.com/forum/discussion/3577/the-lost-heir-wip
I wanted to try a multi-episodic project for a few reasons. I liked the idea of building fans of the story that I saw happening with ZE, Waywalkers and Heroes Rise. Basically, to be able to tell a larger story with characters that would continue forward and be looked forward to. To have a little suspense and mystery as people guessed what was going to happen next.
My games seem to naturally fall around the 130k mark, and the first part of The Lost Heir is hovering over that mark as I conclude the first draft. I don’t aim for that number, it just seems to happen. But Lost Heir is bigger and there’s lots to go. I have a good outline of the next two parts and I intend to write a good chunk of part 2 before I even beta test part 1, to make sure I have a good flow set up.
It seems like a bit of a risk though. What if nobody likes the first or second game? Will you push through with it? What if you lose interest yourself? Or what if you don’t like how the story is going or concluding?
As for branching, I abhor false choices and choices with no meaning. So yes, I think your decisions should matter in the first 2 games.
One last thing to keep in mind. The success rate of seeing WIPs become finished games is very low. Unfortunately, my guess is that a trilogy would have even longer odds of finishing. So, I’d suggest that you make a single shot game @Harian, and if it ends up becoming a monster of a game, consider splitting it up after the fact.