Initial phone conversation with hiring manager followed by 3 hour on site interview with 4 people, staggered, in the department. Final stage was to be a 1:1 with company VP which never materialized. Honestly 3 hours isn't too far outside the norm, and I've heard of worse (Amazon), but it was 3 hours without any breaks for bathroom, water, etc. Was ready to be done after that and it definitely had an impact on my interview by the end of the third hour (offer the guy a bottle of water!).
Also: After having received replies to ALL my email thank yous (this never happens, ever) I left with a positive feeling - or at least I'd get to the final stage and meet with their VP. Unfortunately the line of communication then ceased despite multiple follow ups....... Radio silence is never cool, just send a quick email saying you've elected to move on with a different candidate instead of stringing people along!