Consulting - 3rd interview

I am interviewing with a smaller consulting firm for an experienced position (more than 5 years consulting experience) and have been invited back for a 3rd interview. The initial two interviews were only up to an hour long.

The 1st interview with a senior manager covered generalities, and some standard questions on experience/achievements (mostly 'getting to know you' questions). The second was with a senior manager from the specific department, which covered a combination of questions to test what the challenges of the industry, understanding of what kept high-level execs awake at night and to a lesser degree technical questions.

With this 3rd one, the interview is scheduled to take one and a half hours (which I consider quite long; it is after all the 3rd interview). This makes me wonder what the interview would entail and whether there is a curveball.

Does anyone know what the usual interview practices are (if there is such a thing), in consulting or otherwise - in terms of interview scope, content, etc for various stages/legs of the interview esp in 3rd/ latter end of the interview stages? If not, would you venture a guess?

Any additional thoughts/tips would be appreciated. Thanks!

Andrew:

My guess is since this is a smaller company therefore it may have staff from diverse background. And, they all want to have their comfort level with you. After the 3rd interview, they will get together around a round table and share their findings as well as give you some points on certain aspects that they were supposed to look into during the interviews.

If I were you, I would also try to find out that who are you going to report to and also who is the final decision maker in hiring you? Also, are both the above involved in your interviewing process?

Just a few thoughts.