I have posted some pretty long ones and never been told they are too long (unlike PM's that can only ne 3000 characters).
I have broken mine down by the interesting things that happened, and not by days or parks. I don't want them too long beacuase then people will get a little tired of them.
I like the longish cliff hanger type the best! Growin'upDisney has me on the edge of my seat right now! It gives me a reason to check in on the boards every day. You never know when the next part will show up.