It depends if you are interviewing in the booths ('Career Center') or if you are meeting informally in restaurant, hotel, Starbucks. If the former, the interview time has a hard cap - generally 30 min. There will probably be someone who needs to use the booth after you so they will shoo you out. For informal interviews, the time is much more variable. Sometimes only 15 min (rare, but happens if you clearly are not right for the job) to 1.5 hours (also rare, but sometimes you just hit it off with someone). Average 30-40 min, I'd say.