Just found a job after a year of looking for it. I rejected one offer back in May, or June and now I got another one and accepted it. I can tell you from my experience that yeah in most cases it seems at the final interview that a decision has already been made. I think I've had a total of at least 3 final stage interviews and in two cases I knew they already wanted to hire me and in one case I had the feeling they only needed confirmation they didn't want me. I guess they always have to have at least a few candidates in the final stage, even if the decision has been made.