5 hour interview coming up, including 2.5 hour lunch. What should I expect?

Hey r/engineeringstudents,

4th year EE here. (I'm trying to be as vague as possible regarding the company, position, and location on purpose just in case that information could identify me in any way.) After two long phone interviews about my resume and some technical questions, I've been asked to fly out-of-state for an on-site interview this upcoming Thursday. My interviewer mentioned the following times in his email regarding the interview:

Time: 8:30am - 11:00am

Lunch: 11:00am - 1:30pm

I've had long on-site interviews before, but never a lunch interview. 2.5 hours for lunch seems like a lot of time. What should I expect going into this? Thanks so much, I'm doing my best to prepare in the meantime.