I always read all of the posts in a thread. If a thread is more than 3 pages (I have it set to show the highest number of posts on a page, so most threads are only 1-2 pages in my view), and I haven't been following it from the beginning, I probably won't click on it because I don't feel like reading through the whole thing.
The only exception to reading every post is when people start getting chatty in a thread, usually 2 or 3 people just talking back and forth to each other, in which case I skip past their posts and focus on any "real" conversation.
The only exception to reading every post is when people start getting chatty in a thread, usually 2 or 3 people just talking back and forth to each other, in which case I skip past their posts and focus on any "real" conversation.