All the research I've seen seems to draw the conclusion that the only strong predictor of performance in a job -- is past performance.
You are replying to a comment suggesting that there may be value in a process using multiple interviewers over a total time of eight hours.
It could well be that one, some, many, or even all of the multiple people involved use your suggested process and that that it takes a total of eight hours to get a good read on past performance.
Ahha - yeah - I think I started to reply and wandered off topic :)
I think it was more in reply to the OP's original comment about puzzles being a waste of time. I think 8 hours is fine - if it's progressing in the right areas.
I tend not to like panel interviews, but a broad range of interviewers isn't a bad idea - the best interviews I've had usually include walking the floor a bit, seeing the environment, chatting to potential teammates - although I'd worry that it would be hard to get a consensus if too many people are involved.
You are replying to a comment suggesting that there may be value in a process using multiple interviewers over a total time of eight hours.
It could well be that one, some, many, or even all of the multiple people involved use your suggested process and that that it takes a total of eight hours to get a good read on past performance.
So... is your comment orthogonal to mine?